# CVE-2026-125371: Tinyproxy through 1.11.3 Hostname ACL Allow-List Bypass via Suffix Match

Status: published. Published: 2026-11-09. Updated: 2026-11-09.

Tinyproxy through 1.11.3 contains an access control bypass vulnerability in acl_string_processing() in src/acl.c that compares only trailing hostname characters without checking DNS label boundaries. Attackers controlling the PTR record for their source IP, such as untrusted.net, can satisfy an 'Allow trusted.net' entry to use the proxy despite deny-by-default ACLs.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/tinyproxy/tinyproxy/commit/3991ac8f98c6a9f05b3265018b812dbf2ca92c28

## Affected products and versions

- tinyproxy / tinyproxy: ≥ 0; ≤ 1.11.3 (affected, semver); 3991ac8f98c6a9f05b3265018b812dbf2ca92c28 (unaffected, git). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6.3 (medium); CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 4.8 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-187

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/tinyproxy/tinyproxy/issues/627 (CNA: VulnCheck; issue-tracking)

- https://github.com/tinyproxy/tinyproxy (CNA: VulnCheck; product)

- https://github.com/tinyproxy/tinyproxy/blob/1.11.3/src/acl.c#L156-L174 (CNA: VulnCheck; technical-description)

- https://github.com/tinyproxy/tinyproxy/commit/3991ac8f98c6a9f05b3265018b812dbf2ca92c28 (CNA: VulnCheck; patch)

- https://www.vulncheck.com/advisories/tinyproxy-through-1.11.3-hostname-acl-allow-list-bypass-via-suffix-match (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-125371; retrieved 2026-11-10; source updated 2026-11-09

Revision: 643d540ac49653e487f92b19e6426af112dfb1f210bf65212e94cb1b0180c0f6

Canonical: https://y2.dev/cve/CVE-2026-125371

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