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Apache disclosed CVE-2021-25122, an HTTP/2 (h2c) request mix-up flaw in Tomcat that could cause a request to be associated with the wrong response. Under affected HTTP/2 configurations, the defect could expose one user to another user's application response, creating a risk of information disclosure and session or transaction confusion.
The issue affects Tomcat 8.5.0 through 8.5.63, 9.0.0.M1 through 9.0.43, and 10.0.0-M1 through 10.0.2. Organizations should upgrade to Tomcat 8.5.64, 9.0.44, or 10.0.4 or later, and assess applications using HTTP/2 for potential unintended response exposure; Tomcat 7 is not listed among the affected release lines.
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2 events from the most recent confirmed update back to the earliest known activity.
Apache Tomcat added an additional fix for bug 64830, addressing an h2c edge case that could corrupt requests. The change restores leftover input to the socket wrapper before creating or selecting an HTTP upgrade processor, allowing buffered data to be processed correctly.
Apache Tomcat issued a security notice for CVE-2021-25122, described as an h2c request mix-up vulnerability.
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Apache disclosed **CVE-2026-43515**, an improper-authorization flaw in Tomcat’s handling of security constraints. When multiple constraints specify an HTTP method for the same extension pattern, Tomcat may enforce only the first constraint, potentially allowing intended access restrictions to be applied incorrectly. The issue affects Tomcat 9.0.0.M1–9.0.117, 10.1.0-M1–10.1.54, and 11.0.0-M1–11.0.21; MITRE also lists legacy Tomcat 7.0.0–7.0.109 and 8.5.0–8.5.100 as affected. Apache also fixed **CVE-2026-41293**, a low-severity HTTP/2 request-header validation issue that can cause unexpected behavior in applications relying on Servlet API header values being specification-compliant. Organizations should upgrade to Tomcat **9.0.118**, **10.1.55**, or **11.0.22** or later; unsupported releases should be retired or moved to a supported fixed version. Apache had separately disclosed **CVE-2026-32990**, identifying an incomplete prior fix for CVE-2025-66614.
Aug 28, 2026
Apache disclosed **CVE-2026-59083**, a vulnerability in Tomcat's `RewriteValve` caused by incorrect URL decoding of hex-encoded characters that can let attackers bypass security controls in some configurations. The issue is classified as **CWE-177** and was described as low severity by Apache, though the CVE record notes network attackability with low attack complexity, no privileges required, and no user interaction. Apache said the flaw affects supported Tomcat branches **11.0.0-M1 through 11.0.23**, **10.1.0-M1 through 10.1.56**, and **9.0.0.M1 through 9.0.119**, with reports also listing **8.5.0 through 8.5.100** as affected. Apache and downstream advisories urged users to upgrade to fixed releases **11.0.24**, **10.1.57**, or **9.0.120**, while warning that older unsupported versions may also be vulnerable; versions before **8.0.0** were noted as unaffected in the oss-security disclosure. The vulnerability was published through Apache security pages, the Apache mailing list, and `oss-security`, with the CVE entry updated to include affected-version details, a CVSS v3.1 vector, and a CISA SSVC assessment.
Aug 28, 2026
Apache disclosed **CVE-2026-42498**, a low-severity information-disclosure flaw in Tomcat’s WebSocket client. After authenticating a WebSocket request, the client can send its most recent HTTP authentication header to an unexpected redirect-target host, potentially exposing credentials or other sensitive header contents. The vulnerability is classified as `CWE-200`, Exposure of Sensitive Information to an Unauthorized Actor. Affected releases include Tomcat 11.0.0-M1 through 11.0.21, 10.1.0-M1 through 10.1.54, and 9.0.2 through 9.0.117; MITRE also identifies affected version lines including 7.0 and 8.5, which may be unsupported. Organizations should upgrade to Tomcat 11.0.22 or later, 10.1.55 or later, or 9.0.118 or later, and assess WebSocket clients that authenticate before following redirects to external hosts.
Aug 28, 2026