CVE-2026-16434Public exploitNetwork attack vectorHinoki check available

Cookie-path manipulation via backslash prefix bypass

Published Aug 25, 2026 · Updated Aug 27, 2026

Improper input validation in Adminer 4.6.0 through 5.5.0 allows remote attackers to alter cookie-path scoping via X-Forwarded-Prefix. The guard in bootstrap.inc.php accepts a prefix whose second character is a backslash, then prepends it to REQUEST_URI; browser slash normalization lets the resulting network-path reference reach cookie_path() and the Set-Cookie Path attribute. Exploitation requires a client-settable X-Forwarded-Prefix header through a misconfigured or absent reverse proxy, and the documented consequence is limited to anomalous cookie-path scoping.

CVSS severity2.3
Low
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Improper input validation in Adminer 4.6.0 through 5.5.0 allows remote attackers to alter cookie-path scoping via X-Forwarded-Prefix. The guard in bootstrap.inc.php accepts a prefix whose second character is a backslash, then prepends it to REQUEST_URI; browser slash normalization lets the resulting network-path reference reach cookie_path() and the Set-Cookie Path attribute. Exploitation requires a client-settable X-Forwarded-Prefix header through a misconfigured or absent reverse proxy, and the documented consequence is limited to anomalous cookie-path scoping.

The record

CVE
CVE-2026-16434
Published
Aug 25, 2026
Updated
Aug 27, 2026
Vendor
Adminer
Product
Adminer
Classifications
CWE-20
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <5.5.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Adminer · Adminerversion=0 <5.5.1

Published CVSS scores

2.3GitHubCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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