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Adminer CVE-2026-16434

| EUVDEUVD-2026-65195 LOW
Improper Input Validation (CWE-20)
2026-08-25 VulnCheck GHSA-jh7j-hfxx-jv6m
PHP Information Disclosure Adminer
2.3
CVSS 4.0 · Vendor: VulnCheck

Severity by source

Vendor (VulnCheck) PRIMARY
2.3 LOW
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
3.1 LOW

Network vector with high complexity (proxy misconfiguration required), no privileges needed, user interaction required; integrity impact limited to cookie-path scoping only.

3.1 AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N
4.0 AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
P
Scope
X

Lifecycle Timeline

2
Patch available
Aug 25, 2026 - 03:16 EUVD
Analysis Generated
Aug 25, 2026 - 02:34 vuln.today

DescriptionCVE.org

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.

AnalysisAI

Cookie-path scoping manipulation in Adminer 4.6.0-5.5.0 results from an incomplete fix for a prior X-Forwarded-Prefix header injection (GHSA-8478-xrj3-h9c2). The validation guard in bootstrap.inc.php blocks double-slash prefixes (//evil.com) but accepts backslash variants (/\evil.com); because browsers normalize backslash to forward slash, the malformed prefix survives as a network-path reference into cookie_path(), corrupting the Set-Cookie Path attribute. …

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Vulnerability AssessmentAI

Exploitation Exploitation requires two simultaneous conditions: (1) the reverse proxy in front of Adminer is misconfigured or absent, allowing clients to supply an arbitrary X-Forwarded-Prefix header that is forwarded unmodified to Adminer; (2) user interaction is required (the browser must process the malformed Set-Cookie response). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 4.0 score of 2.3 (Very Low) is well-calibrated for this issue: attack complexity is high (AC:H) because exploitation requires a misconfigured or absent reverse proxy - a condition that should not exist in hardened deployments - and user interaction is required (UI:P). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade to Adminer 5.5.1, which contains the corrected validation logic for the X-Forwarded-Prefix header, per the vendor advisory at https://github.com/vrana/adminer/security/advisories/GHSA-fr74-9mf9-gf44. … Detailed patch versions, workarounds, and compensating controls in full report.
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CVE-2026-16434 vulnerability details – vuln.today
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