Vulnerability · Published Jul 29, 2026 · Assigned by apache

CVE-2026-65100Apache Traffic Server: HPACK encoder desynchronizes from the decoder after a failed header encode

Medium 4.8

In plain English

A medium-severity security flaw in Apache Traffic Server from Apache Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 48% of all known vulnerabilities).

Severity (CVSS 3.1)4.8Medium

Exploit odds (30 days)0.6%top 52.1% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	trafficserver	no fix listed	DEBIAN-CVE-2026-65100
Ubuntu:24.04:LTS	trafficserver	no fix listed	UBUNTU-CVE-2026-65100

Affected products (as reported)

Vendor	Product	Versions
Apache Software Foundation	Apache Traffic Server	8.0.0 – through 8.1.119.0.0 – through 9.2.1410.0.0 – through 10.1.3

Weakness: CWE-696 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L

References

https://lists.apache.org/thread/5prl9glcm9g2swnq9hqxvnokylm1gr6d vendor-advisory