Description
Apache Traffic Server can be used to exhaust an HTTP/1.1 origin's worker pool via a malformed padded HTTP/2 DATA frame.



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.
Published: 2026-10-21
Score: 7.7 High
EPSS: n/a
KEV: No
Impact: Denial of Service
Action: Immediate Patch
AI Analysis

Impact

Apache Traffic Server can be exploited through a malformed HTTP/2 DATA frame with padded content that causes a padding underflow (CWE-191). The underflow triggers the server to allocate many backend worker threads for the origin, exhausting the worker pool and forcing the system to become unable to process legitimate requests. This impact manifests as a denial of service to users of the affected server.

Affected Systems

The vulnerability affects Apache Traffic Server versions 8.0.0 through 8.1.11, 9.0.0 through 9.2.15, 10.0.0 through 10.1.4, and 10.2.0, as supplied by the Apache Software Foundation.

Risk and Exploitability

With a CVSS score of 7.7 and no available EPSS data, the risk is considered moderate; the vulnerability is not listed in the CISA KEV catalog and no public exploits are documented. The likely attack vector is remote via the network from a client sending crafted HTTP/2 frames. An attacker can remotely trigger the worker pool exhaustion, leading to service disruption for all downstream clients.

Generated by OpenCVE AI on October 22, 2026 at 01:46 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade Apache Traffic Server to a patched version such as 9.2.16, 10.1.5, or 10.2.1.
  • If an immediate upgrade is not possible, limit or filter incoming HTTP/2 traffic to reduce repeated padding usage, and monitor worker pool consumption for signs of exhaustion.
  • Consider disabling HTTP/2 on the server or placing the Traffic Server behind a proxy that terminates HTTP/2 before forwarding to the origin.

Generated by OpenCVE AI on October 22, 2026 at 01:46 UTC.

Tracking

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Advisories

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History

Wed, 21 Oct 2026 19:30:00 +0000

Type Values Removed Values Added
Description Apache Traffic Server can be used to exhaust an HTTP/1.1 origin's worker pool via a malformed padded HTTP/2 DATA frame. 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.
Title Apache Traffic Server: HTTP/2 DATA frame padding underflow lets a client trigger backend worker-pool exhaustion
Weaknesses CWE-191
References
Metrics cvssV3_1

{'score': 8.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H'}

cvssV4_0

{'score': 7.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:H'}

Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: apache

Published:

Updated: 2026-10-21T19:11:59.516Z

Reserved: 2026-10-16T20:19:38.638Z

Link: CVE-2026-111808

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-21T20:17:22.427

Modified: 2026-10-21T20:17:22.427

Link: CVE-2026-111808

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-22T02:00:10Z

Weaknesses
  • CWE-191

    Integer Underflow (Wrap or Wraparound)