● Zion Boggan
repos/security-portfolio/security-research-notebook/email-enumeration-timing/index.html
zionboggan.com ↗
Code Commits Tags
288 lines · html
History for this file →
1
<!doctype html>
2
<html lang="en"><head><meta charset="utf-8">
3
<meta name="viewport" content="width=device-width, initial-scale=1.0">
4
<title>Email Enumeration Timing | Zion Boggan</title>
5
<meta name="description" content="`/v1/userauth` timing differential distinguishes registered vs unregistered emails.">
6
<link rel="icon" href="data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 32 32'%3E%3Crect width='32' height='32' rx='6' fill='%230c0e12'/%3E%3Ctext x='16' y='22' font-family='monospace' font-size='15' fill='%236cc7b8' text-anchor='middle'%3Ezb%3C/text%3E%3C/svg%3E">
7
<style>
8
  :root{
9
    --bg:#0c0e12; --bg2:#0f1217; --panel:#14181f; --panel2:#171c24;
10
    --line:#222936; --line2:#2c3543;
11
    --ink:#e8eaed; --soft:#c3cad4; --muted:#8a94a3; --faint:#5d6675;
12
    --accent:#6cc7b8; --accent-dim:#274b47;
13
    --maxw:1020px;
14
  }
15
  *{box-sizing:border-box;}
16
  html{scroll-behavior:smooth;}
17
  body{margin:0;background:var(--bg);color:var(--ink);
18
    font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
19
    font-size:16px;line-height:1.65;-webkit-font-smoothing:antialiased;}
20
  .mono{font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Consolas,monospace;}
21
  a{color:var(--accent);text-decoration:none;}
22
  a:hover{color:#8fe0d2;}
23
  .wrap{max-width:var(--maxw);margin:0 auto;padding:0 24px;}
24
25
  /* nav */
26
  nav{position:sticky;top:0;z-index:20;background:rgba(12,14,18,.82);
27
    backdrop-filter:blur(10px);border-bottom:1px solid var(--line);}
28
  nav .wrap{display:flex;align-items:center;justify-content:space-between;height:58px;}
29
  nav .brand{font-weight:600;letter-spacing:.2px;}
30
  nav .brand .dot{color:var(--accent);}
31
  nav .links{display:flex;gap:26px;font-size:13.5px;}
32
  nav .links a{color:var(--muted);}
33
  nav .links a:hover{color:var(--ink);}
34
  @media(max-width:680px){nav .links{display:none;}}
35
36
  /* hero */
37
  header.hero{padding:74px 0 54px;border-bottom:1px solid var(--line);
38
    background:radial-gradient(900px 380px at 78% -10%, #11201e 0%, transparent 60%);}
39
  .avail{font-size:12.5px;letter-spacing:1.5px;text-transform:uppercase;color:var(--accent);
40
    display:flex;align-items:center;gap:9px;margin-bottom:20px;}
41
  .avail .pulse{width:7px;height:7px;border-radius:50%;background:var(--accent);
42
    box-shadow:0 0 0 0 rgba(108,199,184,.5);animation:p 2.4s infinite;}
43
  @keyframes p{0%{box-shadow:0 0 0 0 rgba(108,199,184,.45)}70%{box-shadow:0 0 0 8px rgba(108,199,184,0)}100%{box-shadow:0 0 0 0 rgba(108,199,184,0)}}
44
  h1{font-size:clamp(34px,6vw,52px);line-height:1.05;margin:0 0 8px;letter-spacing:-1px;font-weight:680;}
45
  .hero .sub{font-size:clamp(16px,2.4vw,20px);color:var(--soft);margin:0 0 24px;font-weight:500;}
46
  .hero .lede{max-width:660px;color:var(--soft);font-size:17px;margin:0 0 28px;}
47
  .hero .lede b{color:var(--ink);font-weight:600;}
48
  .cta{display:flex;flex-wrap:wrap;gap:12px;align-items:center;}
49
  .btn{display:inline-flex;align-items:center;gap:8px;padding:10px 18px;border-radius:8px;
50
    font-size:14.5px;font-weight:550;border:1px solid var(--line2);color:var(--ink);background:var(--panel);}
51
  .btn:hover{border-color:var(--accent-dim);background:var(--panel2);color:var(--ink);}
52
  .btn.primary{background:var(--accent);color:#06231f;border-color:var(--accent);font-weight:650;}
53
  .btn.primary:hover{background:#8fe0d2;color:#06231f;}
54
  .meta{margin-top:26px;display:flex;flex-wrap:wrap;gap:8px 22px;font-size:13px;color:var(--muted);}
55
  .meta .mono{color:var(--faint);}
56
57
  /* sections */
58
  section{padding:64px 0;border-bottom:1px solid var(--line);}
59
  .shead{display:flex;align-items:baseline;gap:14px;margin-bottom:30px;}
60
  .shead .idx{font-size:13px;color:var(--accent);letter-spacing:1px;}
61
  .shead h2{font-size:14px;letter-spacing:2px;text-transform:uppercase;color:var(--muted);margin:0;font-weight:600;}
62
  .shead .rule{flex:1;height:1px;background:var(--line);}
63
64
  /* flagship */
65
  .flag{background:linear-gradient(180deg,var(--panel) 0%,var(--bg2) 100%);
66
    border:1px solid var(--line2);border-radius:14px;overflow:hidden;}
67
  .flag .top{padding:30px 32px 8px;}
68
  .flag .tag{font-size:12px;letter-spacing:1.5px;text-transform:uppercase;color:var(--accent);margin-bottom:12px;}
69
  .flag h3{font-size:27px;margin:0 0 6px;letter-spacing:-.4px;}
70
  .flag h3 .v{font-size:13px;color:var(--muted);font-weight:500;margin-left:8px;letter-spacing:0;}
71
  .flag .grid{display:grid;grid-template-columns:1.25fr 1fr;gap:30px;padding:14px 32px 30px;}
72
  .flag p{color:var(--soft);margin:0 0 16px;}
73
  .flag .stats{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-top:6px;}
74
  .stat{background:var(--bg);border:1px solid var(--line);border-radius:9px;padding:13px 15px;}
75
  .stat .n{font-size:21px;font-weight:680;color:var(--ink);}
76
  .stat .k{font-size:12px;color:var(--muted);margin-top:2px;}
77
  .spec{background:var(--bg);border:1px solid var(--line);border-radius:10px;padding:18px 18px;}
78
  .spec .sk{font-size:11px;letter-spacing:1.5px;text-transform:uppercase;color:var(--faint);margin-bottom:10px;}
79
  .spec ul{margin:0;padding:0;list-style:none;font-size:13.5px;}
80
  .spec li{padding:6px 0;border-top:1px solid var(--line);color:var(--soft);display:flex;justify-content:space-between;gap:14px;}
81
  .spec li:first-child{border-top:none;}
82
  .spec li span{color:var(--muted);}
83
  .flag .foot{padding:0 32px 28px;display:flex;gap:18px;flex-wrap:wrap;font-size:14px;}
84
  @media(max-width:720px){.flag .grid{grid-template-columns:1fr;}}
85
86
  /* lab cards */
87
  .cards{display:grid;grid-template-columns:1fr 1fr;gap:20px;}
88
  @media(max-width:680px){.cards{grid-template-columns:1fr;}}
89
  .card{border:1px solid var(--line);border-radius:12px;overflow:hidden;background:var(--panel);
90
    display:flex;flex-direction:column;transition:border-color .15s,transform .15s;}
91
  .card:hover{border-color:var(--accent-dim);transform:translateY(-2px);}
92
  .card .thumb{height:172px;overflow:hidden;border-bottom:1px solid var(--line);background:#fff;}
93
  .card .thumb img{width:100%;height:100%;object-fit:cover;object-position:top left;display:block;}
94
  .card .body{padding:18px 20px 20px;display:flex;flex-direction:column;flex:1;}
95
  .card h3{margin:0 0 9px;font-size:17px;}
96
  .card p{margin:0 0 14px;font-size:14px;color:var(--soft);flex:1;}
97
  .tags{display:flex;flex-wrap:wrap;gap:6px;margin-bottom:14px;}
98
  .tags span{font-size:11.5px;color:var(--muted);background:var(--bg);border:1px solid var(--line);
99
    border-radius:5px;padding:3px 8px;}
100
  .card .lnk{font-size:13.5px;font-family:ui-monospace,Menlo,monospace;}
101
  .card .lnk::after{content:" →";}
102
103
  /* research */
104
  .rlede{color:var(--soft);max-width:680px;margin:-6px 0 26px;}
105
  .research{display:flex;flex-direction:column;gap:0;border:1px solid var(--line);border-radius:12px;overflow:hidden;}
106
  .ritem{display:grid;grid-template-columns:120px 1fr auto;gap:18px;align-items:center;
107
    padding:18px 22px;border-top:1px solid var(--line);}
108
  .ritem:first-child{border-top:none;}
109
  .ritem:hover{background:var(--panel);}
110
  .ritem .cls{font-size:11px;letter-spacing:.5px;text-transform:uppercase;color:var(--accent);}
111
  .ritem h3{margin:0 0 3px;font-size:16px;}
112
  .ritem p{margin:0;font-size:13.5px;color:var(--muted);}
113
  .ritem .go{font-family:ui-monospace,Menlo,monospace;font-size:13px;white-space:nowrap;}
114
  @media(max-width:680px){.ritem{grid-template-columns:1fr;gap:6px;}.ritem .go{margin-top:4px;}}
115
  .progs{margin-top:22px;}
116
  .progs .sk{font-size:11px;letter-spacing:1.5px;text-transform:uppercase;color:var(--faint);margin-bottom:11px;}
117
  .progs .row{display:flex;flex-wrap:wrap;gap:7px;}
118
  .progs .row span{font-size:12.5px;color:var(--soft);background:var(--panel);border:1px solid var(--line);
119
    border-radius:6px;padding:4px 10px;}
120
121
  /* credentials */
122
  .cred{display:grid;grid-template-columns:1.1fr 1fr;gap:28px;}
123
  @media(max-width:680px){.cred{grid-template-columns:1fr;}}
124
  .cred p{color:var(--soft);margin:0 0 14px;}
125
  .cred .role{font-size:14px;color:var(--muted);}
126
  .cred .role b{color:var(--ink);font-weight:600;}
127
  .certs{list-style:none;margin:0;padding:0;}
128
  .certs li{padding:9px 0;border-top:1px solid var(--line);font-size:14px;color:var(--soft);
129
    display:flex;gap:10px;align-items:baseline;}
130
  .certs li:first-child{border-top:none;}
131
  .certs li .c{color:var(--accent);font-family:ui-monospace,Menlo,monospace;font-size:12px;}
132
133
  footer{padding:46px 0 64px;}
134
  footer .row{display:flex;flex-wrap:wrap;justify-content:space-between;gap:18px;align-items:center;}
135
  footer .links a{color:var(--soft);margin-right:20px;font-size:14px;}
136
  footer .note{color:var(--faint);font-size:12.5px;max-width:520px;}
137
138
  .detail-hero{padding:40px 0 26px;}
139
  .back{display:inline-block;font-size:13px;color:var(--muted);margin-bottom:20px;font-family:ui-monospace,Menlo,monospace;}
140
  .back:hover{color:var(--ink);}
141
  .kicker{font-size:12px;letter-spacing:2px;text-transform:uppercase;color:var(--accent);margin-bottom:13px;font-family:ui-monospace,Menlo,monospace;}
142
  .detail-hero h1{font-size:clamp(26px,4.6vw,38px);margin:0 0 12px;letter-spacing:-.5px;}
143
  .detail-hero .tagline{font-size:clamp(15px,2vw,18px);color:var(--soft);max-width:800px;margin:0 0 16px;}
144
  .facts{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:12px;margin-top:22px;}
145
  .content{padding:8px 0 0;max-width:840px;}
146
  .content h1{font-size:24px;margin:40px 0 14px;letter-spacing:-.4px;color:var(--ink);}
147
  .content h2{font-size:13px;letter-spacing:2px;text-transform:uppercase;color:var(--muted);margin:42px 0 15px;font-weight:600;border-top:1px solid var(--line);padding-top:28px;}
148
  .content h3{font-size:17px;margin:28px 0 10px;color:var(--ink);font-weight:600;}
149
  .content h4{font-size:14px;margin:22px 0 8px;color:var(--soft);font-weight:600;text-transform:uppercase;letter-spacing:.5px;}
150
  .content p{color:var(--soft);margin:0 0 15px;}
151
  .content ul,.content ol{color:var(--soft);margin:0 0 15px;padding-left:22px;}
152
  .content li{margin:5px 0;}
153
  .content strong{color:var(--ink);font-weight:600;}
154
  .content a{color:var(--accent);}
155
  .content code{font-family:ui-monospace,Menlo,monospace;font-size:12.8px;background:var(--panel2);border:1px solid var(--line);border-radius:4px;padding:1px 5px;color:var(--soft);}
156
  .content pre{background:var(--bg2);border:1px solid var(--line2);border-radius:10px;padding:15px 18px;overflow-x:auto;margin:0 0 18px;}
157
  .content pre code{background:none;border:none;padding:0;font-size:12.4px;color:var(--soft);line-height:1.6;white-space:pre;}
158
  .content table{width:100%;border-collapse:collapse;margin:2px 0 20px;font-size:13.3px;}
159
  .content th{text-align:left;color:var(--muted);font-weight:600;border-bottom:1px solid var(--line2);padding:9px 12px;font-size:11px;letter-spacing:.6px;text-transform:uppercase;}
160
  .content td{color:var(--soft);border-bottom:1px solid var(--line);padding:9px 12px;vertical-align:top;}
161
  .content blockquote{border-left:3px solid var(--accent-dim);margin:0 0 16px;padding:2px 0 2px 18px;color:var(--muted);}
162
  .content hr{border:none;border-top:1px solid var(--line);margin:30px 0;}
163
  /* notebook index */
164
  .nbgroup{margin:40px 0 0;}
165
  .nbgroup h2{font-size:13px;letter-spacing:2px;text-transform:uppercase;color:var(--accent);margin:0 0 4px;font-weight:600;}
166
  .nbgroup .gd{color:var(--faint);font-size:13px;margin:0 0 14px;}
167
  .nbtable{width:100%;border-collapse:collapse;font-size:14px;border:1px solid var(--line);border-radius:12px;overflow:hidden;}
168
  .nbtable tr{border-top:1px solid var(--line);}
169
  .nbtable tr:first-child{border-top:none;}
170
  .nbtable tr:hover{background:var(--panel);}
171
  .nbtable td{padding:14px 16px;vertical-align:top;}
172
  .nbtable .cls{white-space:nowrap;color:var(--accent);font-family:ui-monospace,Menlo,monospace;font-size:11.5px;text-transform:uppercase;letter-spacing:.5px;width:150px;}
173
  .nbtable .ti a{font-weight:600;color:var(--ink);}
174
  .nbtable .ti a:hover{color:var(--accent);}
175
  .nbtable .ol{color:var(--muted);font-size:13px;margin-top:3px;}
176
  @media(max-width:680px){.nbtable .cls{width:auto;display:block;}}
177
</style>
178
<link rel="canonical" href="https://zionboggan.com/security-research-notebook/email-enumeration-timing/">
179
<meta name="author" content="Zion Boggan">
180
<meta name="robots" content="index, follow, max-image-preview:large">
181
<meta property="og:type" content="article">
182
<meta property="og:site_name" content="Zion Boggan">
183
<meta property="og:title" content="Email Enumeration Timing | Zion Boggan">
184
<meta property="og:description" content="`/v1/userauth` timing differential distinguishes registered vs unregistered emails.">
185
<meta property="og:url" content="https://zionboggan.com/security-research-notebook/email-enumeration-timing/">
186
<meta property="og:image" content="https://zionboggan.com/assets/og-default.png">
187
<meta name="twitter:card" content="summary_large_image">
188
<meta name="twitter:title" content="Email Enumeration Timing | Zion Boggan">
189
<meta name="twitter:description" content="`/v1/userauth` timing differential distinguishes registered vs unregistered emails.">
190
<meta name="twitter:image" content="https://zionboggan.com/assets/og-default.png">
191
<script type="application/ld+json">{"@context":"https://schema.org","@type":"TechArticle","headline":"Email Enumeration Timing","description":"`/v1/userauth` timing differential distinguishes registered vs unregistered emails.","url":"https://zionboggan.com/security-research-notebook/email-enumeration-timing/","image":"https://zionboggan.com/assets/og-default.png","author":{"@type":"Person","name":"Zion Boggan","url":"https://zionboggan.com"},"publisher":{"@type":"Person","name":"Zion Boggan"}}</script>
192
</head><body>
193
<nav><div class="wrap">
194
  <a class="brand mono" href="/" style="color:var(--ink)">zion_boggan<span class="dot">.</span></a>
195
  <span class="links"><a href="/#oversight">Oversight</a><a href="/#labs">Labs</a><a href="/#research">Research</a><a href="/security-research-notebook/">Notebook</a><a href="/">Home</a></span>
196
</div></nav>
197
<header class="hero detail-hero"><div class="wrap">
198
  <a class="back" href="/security-research-notebook/">&larr; Research notebook</a>
199
  <div class="kicker">Info disclosure</div>
200
  <h1>Email Enumeration Timing</h1>
201
</div></header>
202
<section><div class="wrap"><div class="content">
203
<h1>SUBMISSION 2</h1>
204
<p>TITLE: User Email Enumeration via /v1/userauth Error Message and Timing Difference</p>
205
<p>TARGET: api.aiven.io (https://api.aiven.io/login)</p>
206
<p>VRT CATEGORY: Broken Authentication and Session Management &gt; Username/Email Enumeration &gt; Non-Brute Force</p>
207
<p>URL: https://api.aiven.io/v1/userauth</p>
208
<h2>DESCRIPTION:</h2>
209
<h2>Summary</h2>
210
<p>The login endpoint <code>POST /v1/userauth</code> returns different error messages and response times for registered vs unregistered email addresses, enabling unauthenticated user enumeration.</p>
211
<ul>
212
<li>Non-existent email: <code>"User does not exist"</code>, ~150ms response</li>
213
<li>Existing email: <code>"user_password_compromised"</code>, ~2,500-5,200ms response</li>
214
</ul>
215
<p>The dual oracle (message + timing) makes enumeration highly reliable. Notably, the password reset endpoint (<code>/v1/user/password_reset_request</code>) is properly implemented and returns a uniform response regardless of email existence.</p>
216
<h2>Steps to Reproduce</h2>
217
<ol>
218
<li>Send a request with a non-existent email:</li>
219
</ol>
220
<pre><code class="language-bash">curl -s -w &quot;\nTime: %{time_total}s&quot; -X POST https://api.aiven.io/v1/userauth \
221
  -H &quot;Content-Type: application/json&quot; \
222
  -d '{&quot;email&quot;:&quot;definitelynotarealuserxyz123@nonexistentdomain99887.com&quot;,&quot;password&quot;:&quot;test123&quot;}'
223
</code></pre>
224
<p><strong>Response:</strong> HTTP 403, ~150-477ms</p>
225
<pre><code class="language-json">{&quot;errors&quot;:[{&quot;message&quot;:&quot;User does not exist&quot;,&quot;status&quot;:403}]}
226
</code></pre>
227
<ol start="2">
228
<li>Send a request with a known existing email:</li>
229
</ol>
230
<pre><code class="language-bash">curl -s -w &quot;\nTime: %{time_total}s&quot; -X POST https://api.aiven.io/v1/userauth \
231
  -H &quot;Content-Type: application/json&quot; \
232
  -d '{&quot;email&quot;:&quot;admin@aiven.io&quot;,&quot;password&quot;:&quot;wrongpassword123!&quot;}'
233
</code></pre>
234
<p><strong>Response:</strong> HTTP 403, ~5,225ms</p>
235
<pre><code class="language-json">{&quot;errors&quot;:[{&quot;error_code&quot;:&quot;user_password_compromised&quot;,&quot;message&quot;:&quot;Your login is blocked because your password is no longer safe. Reset your password to log in.&quot;,&quot;status&quot;:403}]}
236
</code></pre>
237
<ol start="3">
238
<li>Additional tests confirming the pattern:</li>
239
</ol>
240
<table>
241
<thead>
242
<tr>
243
<th>Email</th>
244
<th>Message</th>
245
<th>Time</th>
246
<th>Exists?</th>
247
</tr>
248
</thead>
249
<tbody>
250
<tr>
251
<td>fake@nonexistent.com</td>
252
<td>&ldquo;User does not exist&rdquo;</td>
253
<td>~150ms</td>
254
<td>No</td>
255
</tr>
256
<tr>
257
<td>admin@aiven.io</td>
258
<td>&ldquo;user_password_compromised&rdquo;</td>
259
<td>~5,225ms</td>
260
<td>Yes</td>
261
</tr>
262
<tr>
263
<td>info@aiven.io</td>
264
<td>&ldquo;user_password_compromised&rdquo;</td>
265
<td>~2,688ms</td>
266
<td>Yes</td>
267
</tr>
268
<tr>
269
<td>security@aiven.io</td>
270
<td>&ldquo;User does not exist&rdquo;</td>
271
<td>~150ms</td>
272
<td>No</td>
273
</tr>
274
</tbody>
275
</table>
276
<h2>Impact</h2>
277
<p>An attacker can determine which email addresses are registered on Aiven. This enables targeted credential stuffing against confirmed accounts and targeted phishing campaigns impersonating Aiven (e.g., fake password reset emails). The 10-35x timing difference makes automated enumeration reliable even if error messages were normalized.</p>
278
<h2>Root Cause</h2>
279
<p>The API checks email existence before password validation and returns distinct error messages. The timing difference is likely caused by an additional breach database (HIBP) lookup that only occurs for existing accounts.</p>
280
<h2>Suggested Fix</h2>
281
<p>Return a generic <code>"Invalid credentials"</code> message for all authentication failures and normalize response timing.</p>
282
<hr><p style="color:var(--faint);font-size:12.5px;font-family:ui-monospace,Menlo,monospace">Source &middot; github.com/zionboggan/security-research-notebook &middot; writeups/aiven/email-enumeration-timing.md</p>
283
</div></div></section>
284
<footer><div class="wrap row">
285
  <div class="links"><a href="/">Portfolio</a><a href="https://www.linkedin.com/in/zion-boggan">LinkedIn</a><a href="/security-research-notebook/">Notebook</a><a href="mailto:zionboggan0@gmail.com">Email</a></div>
286
  <div class="note">Coordinated-disclosure research. Findings appear here only after the program's disclosure window closed, the patch shipped, or a CVE was published. No customer data was accessed.</div>
287
</div></footer>
288
</body></html>