CVE-2026-120831
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libslirp Networking Process Crash via Queue Pointer Corruption

Publication date: 2026-11-03

Last updated on: 2026-11-03

Assigner: redhat-SADP

Description
A flaw was found in libslirp in if_output(). When moving a session from the fast queue to the batch queue, the code unlinked and reinserted an arbitrary packet via ifm->m_nextpkt instead of the session queue head, corrupting queue pointers. A guest generating burst traffic could crash the host networking process, causing a denial of service.

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Meta Information

Published
2026-11-03
Last Modified
2026-11-03
Generated
2026-11-03
AI Q&A
2026-11-03
EPSS Evaluated
N/A
NVD
CVE-2026-120831

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-787 The product writes data past the end, or before the beginning, of the intended buffer.

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Executive Summary

CVE-2026-120831 is a flaw in libslirp's if_output() function. When moving a session from the fast queue to the batch queue, the code incorrectly processes packets by unlinking and reinserting an arbitrary packet via ifm->m_nextpkt instead of the session queue head. This corrupts queue pointers, leading to crashes in the host networking process.

Detection Guidance

Monitor for crashes in QEMU or slirp4netns processes, especially after guest systems generate burst traffic. Check logs for segmentation faults or queue corruption errors in libslirp-related services.

Impact Analysis

A guest generating burst traffic could crash the host networking process, causing a denial of service. This means the host system may lose network connectivity or crash, disrupting services relying on the affected system.

Compliance Impact

This vulnerability primarily causes a denial of service by crashing the host networking process, which could disrupt critical services. While it does not directly expose or leak data, prolonged downtime may impact systems handling regulated data, potentially violating availability requirements in standards like GDPR or HIPAA.

Mitigation Strategies

Apply security updates from Red Hat once available. Avoid running untrusted guests or limit guest network traffic to reduce burst traffic risks. Monitor for crashes and restart affected services if issues occur.

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