Medium severity · published Jul 29, 2026
CVE-2026-65100
Apache Traffic Server: HPACK encoder desynchronizes from the decoder after a failed header encode
4.8
CVSS
0.6%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 48% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AT
Apache Traffic Server · Apache Software Foundation
8.0.0 through 8.1.11; 9.0.0 through 9.2.14; 10.0.0 through 10.1.3 · source: vendor
TS
Traffic Server · Apache
8.0.0 through 8.1.9; 9.0.0 before 9.2.15; 10.0.0 before 10.1.4 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-65100
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-65100
vendor-advisory
https://lists.apache.org/thread/5prl9glcm9g2swnq9hqxvnokylm1gr6d
More from Apache Traffic Server
10.0
CVE-2026-111812
Apache Traffic Server: origin_server_auth signs client-controlled AWS headers under the proxy's IAM credentials
10.0
CVE-2026-111815
Apache Traffic Server: TLS session ticket resumption bypasses per-SNI verify_client STRICT enforcement
10.0
CVE-2026-111814
Apache Traffic Server: Default server_session_sharing.match omits MASK_CERT, allowing pooled mTLS identity confusion at the origin
10.0
CVE-2026-111813
Apache Traffic Server: magick plugin passes client query strings unfiltered to ImageMagick convert in the default configuration
10.0
CVE-2026-58162
Apache Traffic Server: Certifier plugin trusts client SNI when generating certificates