# CVE-2026-120831: Libslirp: libslirp: queue pointer corruption in if_output() leading to denial of service

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

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.

## Remediation

- workaround: Red Hat is not aware of a practical temporary workaround that fully mitigates this issue or meets Red Hat Product Security's standards for usability, deployment, applicability, or stability. Customers are advised to apply the relevant security updates when/if they become available. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (libslirp): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (container-tools:rhel8/libslirp): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (libslirp): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (libslirp): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-8): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 5 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 6.5 (medium); CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-787

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/security/cve/CVE-2026-120831 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2565425 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://gitlab.freedesktop.org/slirp/libslirp/-/commit/bad35bd3b529dc47aa109980a69a36da7848ab76 (CNA: redhat)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-120831; retrieved 2026-11-03; source updated 2026-11-03

Revision: 0ca86e042ae1519522d197212f39aef76c9c3f9f6ad318a8f75f9d8cd56bcab7

Canonical: https://y2.dev/cve/CVE-2026-120831

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