# CVE-2025-55702: Apache Traffic Server HTTP request smuggling via Expect: 100-continue

Source: https://junglewise.ai/threats/cve-2025-55702-when-a-client-sends-a-post-with-expect-100-continue-and-the  
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-2025-55702 · Severity: high · CVSS 8.7 · Published 2026-10-21

Apache Traffic Server is a reverse proxy and caching server used to accelerate web applications. When a client sends a POST request with "Expect: 100-continue" and the origin server responds before reading the request body, Traffic Server incorrectly parses leftover body data as a new HTTP request. An attacker can exploit this to bypass front-end security controls and cause responses meant for one user to be delivered to another.

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

## Quick answers

**Is CVE-2025-55702 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-55702 being exploited in the wild.

**How severe is CVE-2025-55702?** High severity, with a CVSS score of 8.7, published 21 October 2026.

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

**Is there a fix for CVE-2025-55702?** 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-2025-55702 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2025-55702?** 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

This is an HTTP request smuggling vulnerability arising from improper handling of the "Expect: 100-continue" mechanism. When an origin server sends a response before consuming the client's POST body, Traffic Server treats the unread body bytes as the start of the next request on the client connection. An attacker on the same connection to Traffic Server can inject smuggled requests that bypass front-end proxy validation, leading to response desynchronization across users. The flaw requires the attacker to be positioned behind a shared front-end proxy.

## Affected products

- Apache Traffic Server 8.0.0 through 8.1.11, 9.0.0 through 9.2.15, 10.0.0 through 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)