CVE-2026-4271: Libsoup: libsoup: denial of service via use-after-free in http/2 server
A flaw was found in libsoup, a library for handling HTTP requests. This vulnerability, known as a Use-After-Free, occurs in the HTTP/2 server implementation. A remote attacker can exploit this by sending specially crafted HTTP/2 requests that cause authentication failures. This can lead to the application attempting to access memory that has already been freed, potentially causing application instability or crashes, resulting in a Denial of Service (DoS).
Other sources
Use-After-Free vulnerability in the HTTP/2 server implementation of the libsoup HTTP library. The issue occurs in the onframerecvcallback() function when processing HTTP/2 frames. During header handling, the function increments an internal callback counter and emits signals such as soupservermessagegotheaders(). If a user-defined signal handler disconnects the client connection during this callback (for example due to authentication failure), the associated SoupServerMessageIOHTTP2 object may be destroyed and freed while still referenced by the callback. When execution returns to the callback, it continues to access the freed io object and attempts to update internal state, resulting in a heap use-after-free condition. An attacker can trigger this issue by sending HTTP/2 requests that cause authentication validation failures, potentially leading to application instability or crashes.
— Red Hat
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-4271?
CVE-2026-4271 has been assigned a medium severity rating due to the potential for denial of service via a use-after-free condition.
How do I fix CVE-2026-4271?
To mitigate CVE-2026-4271, ensure you update libsoup to the latest patched version provided by your distribution.
Who is affected by CVE-2026-4271?
CVE-2026-4271 affects users of libsoup, especially those running specific versions on Red Hat Enterprise Linux.
What can an attacker do with CVE-2026-4271?
An attacker can exploit CVE-2026-4271 to cause a denial-of-service by sending specially crafted HTTP/2 requests to the vulnerable server.
Is CVE-2026-4271 related to HTTP/2 server vulnerabilities?
Yes, CVE-2026-4271 specifically pertains to a weakness in the HTTP/2 server implementation within the libsoup library.