Apache Tomcat up to 11.0.25/10.1.59/9.0.121 HTTP/2 Request Processing confused deputy

Summaryinfo

A vulnerability has been found in Apache Tomcat up to 11.0.25/10.1.59/9.0.121 and classified as critical. This issue affects some unknown processing of the component HTTP2 Request Processing. The manipulation leads to confused deputy. This vulnerability is traded as CVE-2026-86350. It is possible to initiate the attack remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Apache Tomcat up to 11.0.25/10.1.59/9.0.121 and classified as critical. This issue affects an unknown part of the component HTTP2 Request Processing. The manipulation with an unknown input leads to a confused deputy vulnerability. Using CWE to declare the problem leads to CWE-441. The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Inconsistent interpretation of HTTP/2 requests ('HTTP Request/Response smuggling') vulnerability in Apache Tomcat caused by a regression in fix for CVE-2026-41293 can trigger request header mix-up. This issue affects Apache Tomcat: from 11.0.22 through 11.0.25, from 10.1.55 through 10.1.59, from 9.0.118 through 9.0.121. Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.

The advisory is shared at lists.apache.org. The identification of this vulnerability is CVE-2026-86350 since 09/07/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/23/2026).

Upgrading to version 11.0.26, 10.1.60 or 9.0.122 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Application Server Software

Vendor

• Apache

Name

• Tomcat

Version

• 9.0.121
• 10.1.0
• 10.1.1
• 10.1.2
• 10.1.3
• 10.1.4
• 10.1.5
• 10.1.6
• 10.1.7
• 10.1.8
• 10.1.9
• 10.1.10
• 10.1.11
• 10.1.12
• 10.1.13
• 10.1.14
• 10.1.15
• 10.1.16
• 10.1.17
• 10.1.18
• 10.1.19
• 10.1.20
• 10.1.21
• 10.1.22
• 10.1.23
• 10.1.24
• 10.1.25
• 10.1.26
• 10.1.27
• 10.1.28
• 10.1.29
• 10.1.30
• 10.1.31
• 10.1.32
• 10.1.33
• 10.1.34
• 10.1.35
• 10.1.36
• 10.1.37
• 10.1.38
• 10.1.39
• 10.1.40
• 10.1.41
• 10.1.42
• 10.1.43
• 10.1.44
• 10.1.45
• 10.1.46
• 10.1.47
• 10.1.48
• 10.1.49
• 10.1.50
• 10.1.51
• 10.1.52
• 10.1.53
• 10.1.54
• 10.1.55
• 10.1.56
• 10.1.57
• 10.1.58
• 10.1.59
• 11.0.0
• 11.0.1
• 11.0.2
• 11.0.3
• 11.0.4
• 11.0.5
• 11.0.6
• 11.0.7
• 11.0.8
• 11.0.9
• 11.0.10
• 11.0.11
• 11.0.12
• 11.0.13
• 11.0.14
• 11.0.15
• 11.0.16
• 11.0.17
• 11.0.18
• 11.0.19
• 11.0.20
• 11.0.21
• 11.0.22
• 11.0.23
• 11.0.24
• 11.0.25

License

• open-source

Website

• Vendor: https://www.apache.org/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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