CVE-2026-54388: Tinyproxy - HTTP Request Smuggling via Duplicate Content-Length Headers
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
tinyproxyto a version that resolves this vulnerability.Fixed in 1.11.3Patch 364cdb6
Event History
Frequently Asked Questions
What is the severity of CVE-2026-54388?
CVE-2026-54388 has a critical severity rating of 9.1.
How do I fix CVE-2026-54388?
To fix CVE-2026-54388, upgrade Tinyproxy to a version later than 1.11.3 that includes the fix from commit 364cdb6.
What is the impact of CVE-2026-54388?
CVE-2026-54388 allows remote attackers to conduct HTTP request smuggling due to the handling of duplicate Content-Length headers.
Which versions of Tinyproxy are affected by CVE-2026-54388?
Tinyproxy versions up to and including 1.11.3 are affected by CVE-2026-54388.
What type of vulnerability is CVE-2026-54388?
CVE-2026-54388 is classified as an HTTP request smuggling vulnerability.