Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:LSummary
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 46% 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 map to SI-2 (Flaw Remediation) and SC-7 (Boundary Protection) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
A Use-After-Free vulnerability (CWE-416) exists in the HTTP/2 server implementation of libsoup, the GNOME HTTP client/server library. The flaw is triggered when specially crafted requests produce authentication failures, causing the application to reference memory that has already been freed and resulting in instability or crashes.
A remote attacker with no authentication or user interaction can send crafted HTTP/2 requests over the network to trigger the condition. Successful exploitation produces a denial-of-service outcome by crashing the affected process, though it does not impact confidentiality or integrity. The reported CVSS 3.1 base score is 5.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).
Red Hat has published multiple advisories and errata (RHSA-2026:15968, RHSA-2026:17482, RHSA-2026:19143) that address the issue, along with a Bugzilla entry (2448044) and a dedicated CVE page. Administrators should apply the referenced updates to obtain the patched libsoup packages.
EPSS for the CVE reached a peak of 0.0177 before settling at the current value of 0.0093, indicating a modest post-disclosure increase in predicted exploitation interest. No reports of in-the-wild exploitation are included in the supplied references.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-12568
Vulnerability Data
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).
- CWE(s)
Related Threats
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).
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
Mitigating Controls (NIST 800-53 r5) AI
Directly requires timely application of the vendor patches (RHSA-2026 advisories) that eliminate the UAF flaw in libsoup's HTTP/2 handling.
Boundary-protection rules can restrict which remote, unauthenticated sources are allowed to reach the affected HTTP/2 service, reducing the attack surface for crafted requests.
Continuous monitoring of HTTP/2 traffic and process crashes can identify anomalous authentication-failure patterns that trigger the UAF condition.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly incorporate memory-safety tooling and reviews that prevent most use-after-free defects.
Vulnerability identification processes can discover use-after-free issues via scanning or analysis but do not prevent their introduction.
Routine patching removes known use-after-free instances after they have been introduced in released software.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development can detect use-after-free bugs before release.
Secure SDLC mandates memory-safety practices that reduce use-after-free defects.
Application security requirements can specify memory-management rules that mitigate use-after-free.
Secure architecture principles include memory-safety design choices that limit use-after-free exposure.
Secure coding standards directly prescribe avoidance of use-after-free patterns.
Change-management processes help ensure memory-safety fixes are deployed consistently.