Critical-Severity Flaw in Apache Traffic Server Tracked as CVE-2026-111809
A newly published critical vulnerability in Apache Traffic Server carries a CVSS score of 9.3. Here is what is affected and how to respond.
Key points
- CVE-2026-111809 affects Apache Traffic Server.
- CVSS 9.3 (Critical).
- No exploitation confirmed yet.
A critical security flaw tracked as CVE-2026-111809 has been published in the National Vulnerability Database for Apache Traffic Server, with a CVSS base score of 9.3.
At a glance
- CVE
- CVE-2026-111809
- Product
- Apache Traffic Server
- CVSS
- 9.3 Critical
- Weakness
- CWE-444
- Exploited
- No known exploitation
What is the vulnerability?
The NVD entry states: 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.
Affected versions
| Vendor | Product | Versions |
|---|---|---|
| Apache Software Foundation | Apache Traffic Server | up to 8.1.11, up to 9.2.15, up to 10.1.4, 10.2.0 |
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N.
Is it being exploited?
There is no public confirmation of exploitation at the time of publication. It does not appear in CISA's Known Exploited Vulnerabilities catalog. We will update this report if that changes.
What should you do?
- Identify whether the affected product and versions run in your environment.
- Apply the vendor update listed in the advisory as soon as it is available.
- Limit network exposure of the affected service until it is patched.
- Monitor the vendor advisory for updated guidance or exploitation reports.
What to do and how to stay safe: CVE-2026-111809
- Vulnerability severity scores ignore your specific architecture and context.
- Exploitability depends on network exposure and user behavior, not just code flaws.
- Prioritization requires continuous asset inventory and threat intelligence alignment.
Risk-based vulnerability management focuses your limited resources on the flaws that actually threaten your business. Start by mapping your critical assets and checking for active exploits to prioritize your backlog.
Step-by-step guide: Risk-Based Vulnerability Management: Prioritize Fixes by Actual Danger
General security guidance from the Threat Times newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
What is CVE-2026-111809?
CVE-2026-111809 is a CWE-444 vulnerability in Apache Traffic Server.
How severe is CVE-2026-111809?
It has a CVSS score of 9.3 Critical.
Is CVE-2026-111809 being exploited?
There is no public confirmation of exploitation at the time of publication.
