CVE-2026-54388NVD

Vulnerability Summary

Tinyproxy through 1.11.3, fixed in commit 364cdb6, fails to reject requests containing multiple Content-Length headers with differing values, forwarding all duplicate headers to the backend while using the first value to determine how many request body bytes to consume. Remote attackers can desynchronize the proxy and backend parser state, allowing injection of arbitrary HTTP requests to the backend to enable cache poisoning, access control bypass, and request hijacking.

Severity Level

CRITICAL(9.1)

Published Date

Jun 17, 2026

Last Modified

Jul 14, 2026

Exploitation Status

No confirmed exploitation yet

EPSS Score (30-Day)

0.44%Probability

Root Weakness (CWE)

CWE-444: Unknown/Unlisted Weakness ↗

Refer to the official MITRE database for detailed architectural specifications regarding this weakness.

CVSS v4.0 Base Metrics — Score 9.3 (CRITICAL)

Attack VectorNetwork

Attack ComplexityLow

Attack RequirementsNone

Privileges RequiredNone

User InteractionNone

Confidentiality (Vulnerable System)High

Integrity (Vulnerable System)High

Availability (Vulnerable System)None

Confidentiality (Subsequent System)None

Integrity (Subsequent System)None

Availability (Subsequent System)None

CVSS v3.1 Base Metrics — Score 9.1 (CRITICAL)

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

Affected & Patched Versions

Affected Versions

tinyproxy tinyproxy <= 1.11.3

Patched Versions

tinyproxy tinyproxy 1.11.3

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