# CVE-2026-111816: Apache Traffic Server malformed response cache poisoning

Source: https://junglewise.ai/threats/cve-2026-111816-apache-traffic-server-forwarded-a-malformed-302-response-that  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-21. Updated: 2026-10-21  
License: CC BY 4.0 with a link back

CVE-2026-111816 · Severity: critical · CVSS 9.3 · Published 2026-10-21

Apache Traffic Server is a caching proxy that sits between clients and servers to improve performance. A vulnerability in how it validates HTTP responses allows attackers to send malformed responses that the server accepts and caches, which can then be served to other users. This enables cache poisoning and response-framing attacks, potentially delivering malicious content to end users.

Technologies: [Apache Traffic Server](https://junglewise.ai/threats/technologies/traffic-server). Vendors: [Apache](https://junglewise.ai/threats/vendors/apache).

## Quick answers

**Is CVE-2026-111816 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-111816 being exploited in the wild.

**How severe is CVE-2026-111816?** Critical severity, with a CVSS score of 9.3, published 21 October 2026.

**Which products and versions are affected?** Apache Traffic Server 8.0.0–8.1.11, 9.0.0–9.2.15, 10.0.0–10.1.4, 10.2.0.

**Is there a fix for CVE-2026-111816?** Yes: fixed in 9.2.16, 10.1.5, 10.2.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-111816 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-111816?** Check whether you run Apache Traffic Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 9.2.16, 10.1.5, 10.2.1

## Technical details

The vulnerability exists in Traffic Server's HTTP response parsing logic, where a Transfer-Encoding: chunked carve-out bypassed normal parse error rejection for malformed 302 responses. This allows responses that different HTTP peers interpret differently to be cached and served, enabling cache poisoning and HTTP response desynchronization attacks. The flaw affects multiple major versions and requires network access to exploit.

## Affected products

- Apache Traffic Server 8.0.0–8.1.11, 9.0.0–9.2.15, 10.0.0–10.1.4, 10.2.0

## Timeline

- 2026-10-21: disclosed

## References

- [https://lists.apache.org/thread/r95dq29ywcd1f4x30snxlqmb12z4s4kc](https://lists.apache.org/thread/r95dq29ywcd1f4x30snxlqmb12z4s4kc)

## Related threats

- [Apache Traffic Server null pointer dereference in request tear-down](https://junglewise.ai/threats/cve-2026-112381-apache-traffic-server-can-crash-with-a-null-pointer-dereference)
- [Apache Traffic Server connection stall with chunked transfer trailers dropped](https://junglewise.ai/threats/cve-2026-111817-apache-traffic-server-can-stall-a-chunked-transfer-that-it)
- [Apache Traffic Server TLS session resumption bypass of client certificate verification](https://junglewise.ai/threats/cve-2026-111815-apache-traffic-server-can-resume-a-tls-session-across-sni)
- [Apache Traffic Server TLS session reuse with mismatched client certificates](https://junglewise.ai/threats/cve-2026-111814-apache-traffic-server-s-default-outbound-session-sharing-policy)
- [Apache Traffic Server origin_server_auth AWS request signing bypass](https://junglewise.ai/threats/cve-2026-111812-apache-traffic-server-s-origin-server-auth-plugin-lets-a-client)