Vulnerability in Tinyproxy
CVE-2026-54388
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.
Vulnerability class: HTTP Request Smuggling
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.007 (50.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 50.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.007 · change: +0.002
Affected products
- Tinyproxy — versions 0, 364cdb67e0ea00a8e4a7037e2693e0711e816adb
Weakness classification (CWE)
References
- github.com/tinyproxy/tinyproxy/commit/364cdb67e0ea00a8e4a7037e2693e0711e816adb (patch)
- github.com/tinyproxy/tinyproxy/issues/609 (issue-tracking, technical-description)
- github.com/tinyproxy/tinyproxy/pull/610 (issue-tracking)
- www.vulncheck.com/advisories/tinyproxy-http-request-smuggling-via-duplicate-con… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-54388?
- CVE-2026-54388 is a critical-severity vulnerability in Tinyproxy, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 9.1/10. Published 2026-06-17.
- How severe is CVE-2026-54388?
- Critical severity. CVSS v3 base score is 9.1 out of 10.