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CVE-2026-16434— Adminer before 5.5.1 X-Forwarded-Prefix Backslash Bypass

Quick assessment

Affected
vrana adminer
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Adminer 4.6.0 至 5.5.0 版本（该问题已在 5.5.1 版本中修复）存在对先前 X-Forwarded-Prefix 漏洞（GHSA-8478-xrj3-h9c2）的不完整修复。验证逻辑（位于 bootstrap.inc.php）仅拒绝匹配正则表达式 ^/[^/] 的前缀值，即能阻止形如 //evil.com 的请求，但允许类似 /\evil.com 的值（其第二个字符为反斜杠）。由于浏览器会将反斜杠规范化为正斜杠，因此网络路径引用会保留在 REQUEST_URI 中，并最终传递给 cookie_

CVSS 2.3 · Low EPSS 0.30% · P22

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 2

VendorProduct Version RangeStatus
vrana adminer < 5.5.1 affected
5.5.1 unaffected
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I. Basic Information for CVE-2026-16434

Vulnerability Information
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Vulnerability Title
Adminer before 5.5.1 X-Forwarded-Prefix Backslash Bypass
Source: CVE Program / CVE List V5
Vulnerability Description
Adminer 4.6.0 through 5.5.0 (fixed in 5.5.1) contains an incomplete fix for a prior X-Forwarded-Prefix vulnerability (GHSA-8478-xrj3-h9c2). The validation guard (bootstrap.inc.php) only rejects prefixes matching ^/[^/], blocking //evil.com but allowing values such as /\evil.com whose second character is a backslash. Because browsers normalize backslash to forward slash, a network-path reference survives into REQUEST_URI and reaches cookie_path(), affecting the Set-Cookie Path attribute. Exploitation requires that clients can set the X-Forwarded-Prefix header (a misconfigured or absent reverse proxy). Impact is limited to anomalous cookie-path scoping.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
vrana adminer 0 ~ 5.5.1 -

II. Public POCs for CVE-2026-16434

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III. Intelligence Information for CVE-2026-16434

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Vendor Advisories for CVE-2026-16434 (2)

Same Patch Batch · vrana · 2026-08-25 · 10 CVEs total

CVE-2026-56705 9.8 CRITICAL Adminer before 5.4.3 Remote Code Execution via MSSQL PDO DSN Injection
CVE-2026-56702 8.8 HIGH Adminer before 5.4.3 Unrestricted File Upload via AdminerFileUpload
CVE-2026-34968 8.1 HIGH Adminer before 5.4.3 Arbitrary File Deletion via SQLite Drop
CVE-2026-56703 7.2 HIGH Adminer before 5.4.3 Remote Code Execution via SQLite VACUUM INTO
CVE-2026-56706 6.8 MEDIUM Adminer before 5.4.3 CSRF Token Secret Recovery via XOR Masking
CVE-2026-56704 6.1 MEDIUM Adminer before 5.4.3 Cross-Site Scripting via MySQL Version String
CVE-2026-34964 5.8 MEDIUM Adminer before 5.5.0 SSRF via PDO DSN Injection
CVE-2026-34967 5.4 MEDIUM Adminer sql-log Plugin 5.3.0 through 5.4.2 Arbitrary File Write
CVE-2026-34959 4.7 MEDIUM Adminer before 5.5.0 Open Redirect via X-Forwarded-Prefix

IV. Related Vulnerabilities

Same product: adminer
Same vendor: vrana
Same weakness: CWE-20

V. Comments for CVE-2026-16434

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