What is CVE-2026-111809?

CVE-2026-111809 is a critical-severity vulnerability in Apache Software Foundation Traffic Server, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 9.3/10. Published 2026-10-21.

How severe is CVE-2026-111809?

Critical severity. CVSS v3 base score is 9.3 out of 10.

Vulnerability in Apache Software Foundation Traffic Server

CVE-2026-111809

Apache Traffic Server allows request smuggling via HEAD requests that carry Content-Length or Transfer-Encoding. This issue affects Apache Traffic Server: from 8.0.0 through 8.1.11, from 9.0.0 through 9.2.15, from 10.0.0 through 10.1.4, 10.2.0. Users are recommended to upgrade to version 9.2.16, 10.1.5, or 10.2.1, which fix the issue.

Vulnerability class: HTTP Request Smuggling

Published 2026-10-21 · last modified 2026-10-22.

CVSS v3 metric

CVSS v3 base score 9.3 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Apache Software Foundation Traffic Server — versions 10.2.0

Weakness classification (CWE)

CWE-444 — Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling)

References

lists.apache.org/thread/r95dq29ywcd1f4x30snxlqmb12z4s4kc (vendor-advisory)

Frequently asked questions

What is CVE-2026-111809?: CVE-2026-111809 is a critical-severity vulnerability in Apache Software Foundation Traffic Server, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 9.3/10. Published 2026-10-21.
How severe is CVE-2026-111809?: Critical severity. CVSS v3 base score is 9.3 out of 10.