CVE-2026-4271
Published: 17 March 2026
Summary
CVE-2026-4271 is a medium-severity Use After Free (CWE-416) vulnerability in Redhat Enterprise Linux. Its CVSS base score is 5.3 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked in the top 26.9% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly remediates the Use-After-Free flaw in libsoup's HTTP/2 server by requiring timely application of vendor patches as detailed in Red Hat advisories.
Protects against Denial-of-Service from remote crafted HTTP/2 requests causing application crashes by implementing rate limiting and resource throttling.
Mitigates Use-After-Free exploitation through memory protection mechanisms like ASLR and DEP, reducing the likelihood of crashes from accessing freed memory.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Use-after-free in HTTP/2 server leads directly to application crash/DoS via crafted requests, matching T1499.004 (Application or System Exploitation).
NVD Description
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.…
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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).
Deeper analysisAI
CVE-2026-4271 is a Use-After-Free vulnerability (CWE-416) in the HTTP/2 server implementation of libsoup, a library for handling HTTP requests. Published on 2026-03-17, the flaw arises when specially crafted HTTP/2 requests cause authentication failures, leading applications to access memory that has already been freed.
A remote attacker can exploit this vulnerability over the network with low complexity, no privileges, and no user interaction required. By sending the crafted requests, the attacker triggers memory access errors that cause application instability, crashes, or Denial of Service (DoS), consistent with the CVSS v3.1 base score of 5.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).
Red Hat's security advisory (https://access.redhat.com/security/cve/CVE-2026-4271) and Bugzilla entry (https://bugzilla.redhat.com/show_bug.cgi?id=2448044) detail the issue, while the libsoup project's GitLab issues (https://gitlab.gnome.org/GNOME/libsoup/-/issues/496) discuss fixes and mitigation steps for affected versions.
Details
- CWE(s)