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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.

Jakub Vrána Adminer是Jakub Vrána个人开发者的一款轻量级的数据库管理工具。 Jakub Vrána Adminer 4.6.0版本至5.5.0版本存在输入验证错误漏洞，该漏洞源于对X-Forwarded-Prefix的验证不完整，允许包含反斜杠的特定前缀绕过防护，影响Set-Cookie的Path属性，可能导致异常的Cookie路径范围。

CVSS 2.3 · Low EPSS 0.39% · P31

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
Vulnerability Title
Jakub Vrána Adminer 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Jakub Vrána Adminer是Jakub Vrána个人开发者的一款轻量级的数据库管理工具。 Jakub Vrána Adminer 4.6.0版本至5.5.0版本存在输入验证错误漏洞，该漏洞源于对X-Forwarded-Prefix的验证不完整，允许包含反斜杠的特定前缀绕过防护，影响Set-Cookie的Path属性，可能导致异常的Cookie路径范围。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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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