Always-Incorrect Control Flow Implementation vulnerability in Apache Tomcat's rewrite valve meant that if the first condition in an OR chain matched, subsequent non-OR conditions were skipped.

Improper Handling of Case Sensitivity vulnerability in LockOutRealm in Apache Tomcat.

Exposure of HTTP Authentication Header to unexpected hosts during WebSocket authentication vulnerability in Apache Tomcat.

Allocation of Resources Without Limits or Throttling vulnerability in Apache Tomcat.

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in Apache Tomcat via invalid chunk extension.

This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.18, from 10.1.0-M1 through 10.1.52, from 9.0.0.M1 through 9.0.115, from 8.5.0 through 8.5.100, from 7.0.0 through 7.0.109. Other, unsupported versions may also be affected.

Users are recommended to upgrade to version 11.0.20, 10.1.52 or 9.0.116, which fix the issue.

Relative Path Traversal vulnerability in Apache Tomcat.

The fix for bug 60013 introduced a regression where the rewritten URL was normalized before it was decoded. This introduced the possibility that, for rewrite rules that rewrite query parameters to the URL, an attacker could manipulate the request URI to bypass security constraints including the protection for /WEB-INF/ and /META-INF/. If PUT requests were also enabled then malicious files could be uploaded leading to remote code execution. PUT requests are normally limited to trusted users and it is considered unlikely that PUT requests would be enabled in conjunction with a rewrite that manipulated the URI.

This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.10, from 10.1.0-M1 through 10.1.44, from 9.0.0.M11 through 9.0.108.

The following versions were EOL at the time the CVE was created but are known to be affected: 8.5.6 though 8.5.100. Other, older, EOL versions may also be affected. Users are recommended to upgrade to version 11.0.11 or later, 10.1.45 or later or 9.0.109 or later, which fix the issue.

CVE-2025-52434Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') vulnerability in Apache Tomcat when using the APR/Native connector. This was particularly noticeable with client initiated closes of HTTP/2 connections. This issue affects Apache Tomcat: from 9.0.0.M1 through 9.0.106. Users are recommended to upgrade to version 9.0.107, which fixes the issue. CVE-2025-53506Uncontrolled Resource Consumption vulnerability in Apache Tomcat if an HTTP/2 client did not acknowledge the initial settings frame that reduces the maximum permitted concurrent streams. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.8, from 10.1.0-M1 through 10.1.42, from 9.0.0.M1 through 9.0.106. Users are recommended to upgrade to version 11.0.9, 10.1.43 or 9.0.107, which fix the issue.

For some unlikely configurations of multipart upload, an Integer Overflow vulnerability in Apache Tomcat could lead to a DoS via bypassing of size limits.

This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.8, from 10.1.0-M1 through 10.1.42, from 9.0.0.M1 through 9.0.106.

Users are recommended to upgrade to version 11.0.9, 10.1.43 or 9.0.107, which fix the issue.

Authentication Bypass Using an Alternate Path or Channel vulnerability in Apache Tomcat. When using PreResources or PostResources mounted other than at the root of the web application, it was possible to access those resources via an unexpected path. That path was likely not to be protected by the same security constraints as the expected path, allowing those security constraints to be bypassed.

This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.7, from 10.1.0-M1 through 10.1.41, from 9.0.0.M1 through 9.0.105.

Users are recommended to upgrade to version 11.0.8, 10.1.42 or 9.0.106, which fix the issue.

Allocation of Resources Without Limits or Throttling vulnerability in Apache Tomcat.

This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.7, from 10.1.0-M1 through 10.1.41, from 9.0.0.M1 through 9.0.105.

Users are recommended to upgrade to version 11.0.8, 10.1.42 or 9.0.106, which fix the issue.

Improper Handling of Case Sensitivity vulnerability in Apache Tomcat's GCI servlet allows security constraint bypass of security constraints that apply to the pathInfo component of a URI mapped to the CGI servlet.

This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.6, from 10.1.0-M1 through 10.1.40, from 9.0.0.M1 through 9.0.104.

Users are recommended to upgrade to version 11.0.7, 10.1.41 or 9.0.105, which fixes the issue.

Improper Handling of Exceptional Conditions, Uncontrolled Resource Consumption vulnerability in Apache Tomcat. When processing an HTTP/2 stream, Tomcat did not handle some cases of excessive HTTP headers correctly. This led to a miscounting of active HTTP/2 streams which in turn led to the use of an incorrect infinite timeout which allowed connections to remain open which should have been closed.

This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.0-M20, from 10.1.0-M1 through 10.1.24, from 9.0.0-M1 through 9.0.89.

The following versions were EOL at the time the CVE was created but are known to be affected: 8.5.0 though 8.5.100. Other EOL versions may also be affected.

Users are recommended to upgrade to version 11.0.0-M21, 10.1.25 or 9.0.90, which fixes the issue.

Denial of Service due to improper input validation vulnerability for HTTP/2 requests in Apache Tomcat. When processing an HTTP/2 request, if the request exceeded any of the configured limits for headers, the associated HTTP/2 stream was not reset until after all of the headers had been processed.This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.0-M16, from 10.1.0-M1 through 10.1.18, from 9.0.0-M1 through 9.0.85, from 8.5.0 through 8.5.98.

Users are recommended to upgrade to version 11.0.0-M17, 10.1.19, 9.0.86 or 8.5.99 which fix the issue.

Affected versions:

- Apache Tomcat 11.0.0-M1 through 11.0.0-M10 - Apache Tomcat 10.1.0-M1 through 10.1.15 - Apache Tomcat 9.0.0-M1 through 9.0.82 - Apache Tomcat 8.5.0 through 8.5.95

Description:

Improper Input Validation vulnerability in Apache Tomcat.Tomcat from 11.0.0-M1 through 11.0.0-M10, from 10.1.0-M1 through 10.1.15, from 9.0.0-M1 through 9.0.82 and from 8.5.0 through 8.5.95 did not correctly parse HTTP trailer headers. A trailer header that exceeded the header size limit could cause Tomcat to treat a single request as multiple requests leading to the possibility of request smuggling when behind a reverse proxy.

Users are recommended to upgrade to version 11.0.0-M11 onwards, 10.1.16 onwards, 9.0.83 onwards or 8.5.96 onwards, which fix the issue.

Credit:

Norihito Aimoto (OSSTech Corporation) (finder)

References:

https://lists.apache.org/thread/0rqq6ktozqc42ro8hhxdmmdjm1k1tpxr http://www.openwall.com/lists/oss-security/2023/11/28/2

HTTP/2 Rapid reset attack The HTTP/2 protocol allows clients to indicate to the server that a previous stream should be canceled by sending a RSTSTREAM frame. The protocol does not require the client and server to coordinate the cancellation in any way, the client may do it unilaterally. The client may also assume that the cancellation will take effect immediately when the server receives the RSTSTREAM frame, before any other data from that TCP connection is processed.

Abuse of this feature is called a Rapid Reset attack because it relies on the ability for an endpoint to send a RSTSTREAM frame immediately after sending a request frame, which makes the other endpoint start working and then rapidly resets the request. The request is canceled, but leaves the HTTP/2 connection open.

The HTTP/2 Rapid Reset attack built on this capability is simple: The client opens a large number of streams at once as in the standard HTTP/2 attack, but rather than waiting for a response to each request stream from the server or proxy, the client cancels each request immediately.

The ability to reset streams immediately allows each connection to have an indefinite number of requests in flight. By explicitly canceling the requests, the attacker never exceeds the limit on the number of concurrent open streams. The number of in-flight requests is no longer dependent on the round-trip time (RTT), but only on the available network bandwidth.

In a typical HTTP/2 server implementation, the server will still have to do significant amounts of work for canceled requests, such as allocating new stream data structures, parsing the query and doing header decompression, and mapping the URL to a resource. For reverse proxy implementations, the request may be proxied to the backend server before the RSTSTREAM frame is processed. The client on the other hand paid almost no costs for sending the requests. This creates an exploitable cost asymmetry between the server and the client.

Multiple software artifacts implementing HTTP/2 are affected. This advisory was originally ingested from the swift-nio-http2 repo advisory and their original conent follows.

swift-nio-http2 specific advisory swift-nio-http2 is vulnerable to a denial-of-service vulnerability in which a malicious client can create and then reset a large number of HTTP/2 streams in a short period of time. This causes swift-nio-http2 to commit to a large amount of expensive work which it then throws away, including creating entirely new Channels to serve the traffic. This can easily overwhelm an EventLoop and prevent it from making forward progress.

swift-nio-http2 1.28 contains a remediation for this issue that applies reset counter using a sliding window. This constrains the number of stream resets that may occur in a given window of time. Clients violating this limit will have their connections torn down. This allows clients to continue to cancel streams for legitimate reasons, while constraining malicious actors.

Apache Tomcat is vulnerable to HTTP request smuggling, caused by the failure to reject a request containing an invalid Content-Length header when configured to ignore invalid HTTP headers via setting rejectIllegalHeader to false. By sending a specially-crafted request, an attacker could exploit this vulnerability to poison the web cache, bypass web application firewall protection, and conduct XSS attacks.

Apache Tomcat could allow a remote attacker to bypass security restrictions, caused by improper error handling in WebSocket connection. By sending a specially-crafted WebSocket message concurrently with the WebSocket connection closing, an attacker could exploit this vulnerability to continue to use the socket after it has been closed.

A flaw was found in Apache Tomcat. When Tomcat was configured to use NIO+OpenSSL or NIO2+OpenSSL for TLS, a specially crafted packet can trigger an infinite loop, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

Last updated 2 August 2024

A flaw was found in Apache Tomcat. When responding to new h2c connection requests, Apache Tomcat could duplicate request headers and a limited amount of request body from one request to another meaning user A and user B could both see the results of user A's request. The highest threat from this vulnerability is to data confidentiality.

A specially crafted sequence of HTTP/2 requests could trigger high CPU usage for several seconds. If a sufficient number of such requests were made on concurrent HTTP/2 connections, the server could become unresponsive.

Reference: https://tomcat.apache.org/security-8.html

Apache Tomcat could allow a local attacker to hijack a user's session. By using the FORM authentication function, an attacker could exploit this vulnerability to gain access to another user's session.

A privilege escalation flaw was found in Tomcat when the JMX Remote Lifecycle Listener was enabled. A local attacker without access to the Tomcat process or configuration files could be able to manipulate the RMI registry to perform a man-in-the-middle attack. The attacker could then capture user names and passwords used to access the JMX interface and gain complete control over the Tomcat instance.

Last updated 25 August 2025