CVE-2026-65100 Apache Traffic Server: HPACK encoder desynchronizes from the decoder after a failed header encode
An HPACK encoder desynchronization in Apache Traffic Server corrupts subsequent header blocks, potentially disrupting HTTP/2 connections.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-65100?
CVE-2026-65100 is a medium-severity denial of service vulnerability in Apache Traffic Server, published on 29 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Apache Traffic Server updates the HTTP/2 HPACK dynamic table before confirming the header block encoded successfully, so an encode failure leaves the encoder out of sync with the peer decoder and corrupts subsequent header blocks on the connection.
This issue affects Apache Traffic Server: from 8.0.0 through 8.1.11, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.
Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.
Weakness: CWE-696
Which versions are affected by CVE-2026-65100?
It affects 1 product.
Products include Apache Traffic Server.
How do I fix CVE-2026-65100?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-65100 being exploited?
There is no known exploitation of CVE-2026-65100 in the wild and no public exploit code.
Other vulnerabilities in Apache Traffic Server
Sources
Also known as DEBIAN-CVE-2026-65100, GHSA-c6fq-3mhw-8g4j, UBUNTU-CVE-2026-65100.