Apache Traffic Server up to 8.1.11/9.2.15/10.1.4/10.2.0 improper synchronization

Summaryinfo

A vulnerability was found in Apache Traffic Server up to 8.1.11/9.2.15/10.1.4/10.2.0. It has been classified as critical. The affected element is an unknown function. Performing a manipulation results in improper synchronization. This vulnerability is reported as CVE-2025-55702. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as critical, was found in Apache Traffic Server up to 8.1.11/9.2.15/10.1.4/10.2.0. This affects an unknown code block. The manipulation with an unknown input leads to a improper synchronization vulnerability. CWE is classifying the issue as CWE-662. The product utilizes multiple threads or processes to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

When a client sends a POST with Expect: 100-continue and the origin answers before reading the body, Apache Traffic Server parses the unread body left on the client connection as the next request. An attacker behind a front-end proxy that shares connections to Traffic Server can use this to smuggle requests past the front end and desynchronize responses for other users. 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.

It is possible to read the advisory at lists.apache.org. This vulnerability is uniquely identified as CVE-2025-55702 since 08/14/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/21/2026).

Upgrading to version 9.2.16, 10.1.5 or 10.2.1 eliminates this vulnerability.

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Productinfo

Vendor

• Apache

Name

• Traffic Server

Version

• 8.1.0
• 8.1.1
• 8.1.2
• 8.1.3
• 8.1.4
• 8.1.5
• 8.1.6
• 8.1.7
• 8.1.8
• 8.1.9
• 8.1.10
• 8.1.11
• 9.2.0
• 9.2.1
• 9.2.2
• 9.2.3
• 9.2.4
• 9.2.5
• 9.2.6
• 9.2.7
• 9.2.8
• 9.2.9
• 9.2.10
• 9.2.11
• 9.2.12
• 9.2.13
• 9.2.14
• 9.2.15
• 10.0
• 10.1
• 10.1.0
• 10.1.1
• 10.1.2
• 10.1.3
• 10.1.4
• 10.2.0

License

• open-source

Website

• Vendor: https://www.apache.org/

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