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CVE-2026-54387

9.1 · CRITICAL

Tinyproxy through 1.11.3, fixed in commit ff45d3b, fails to reconcile conflicting Content-Length and Transfer-Encoding: chunked headers, forwarding both verbatim to the backend while using Content-…

Published Jun 17, 2026CWE-444EPSS 0.68%

Overview

CVE-2026-54387 is a critical-severity vulnerability. It was published on June 17, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

Tinyproxy through 1.11.3, fixed in commit ff45d3b, fails to reconcile conflicting Content-Length and Transfer-Encoding: chunked headers, forwarding both verbatim to the backend while using Content-Length 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/tinyproxy/tinyproxy/commit/ff45d3bf0e61d0f8ed97ab379d3047f04eb67521GitHubgithub.com/tinyproxy/tinyproxy/issues/609GitHubgithub.com/tinyproxy/tinyproxy/pull/610Refwww.vulncheck.com/advisories/tinyproxy-http-request-smuggling-via-cl-te-desynchronization

How CyberStrike helps

Frequently asked questions

What is CVE-2026-54387?

CVE-2026-54387 is a critical-severity vulnerability. It was published on June 17, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-54387?

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-54387?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-54387?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-54387 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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