CVE-2026-65100

Apache Traffic Server: HPACK encoder desynchronizes from the decoder after a failed header encode

State: Published
Severity: 6.3 Medium
Published: Jul 29, 2026
Updated: Oct 1, 2026
Reserved: Jul 21, 2026

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.

Scores

CVSS	Score	Vector	Source
4.0	6.3 Medium	CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N	apache
3.1	4.8 Medium	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L	apache

Weaknesses

CWE-696 Incorrect Behavior Order

Affected Products

Product	Versions
Apache Traffic ServerApache Software Foundation	8.0.0 through 8.1.11Affected 9.0.0 through 9.2.14Affected 10.0.0 through 10.1.3Affected

References

https://lists.apache.org/thread/5prl9glcm9g2swnq9hqxvnokylm1gr6dvendor-advisory

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