CVE-2026-120830

Libslirp: libslirp: out-of-bounds heap read in icmp_forward_error() leading to information disclosure

Published Nov 3, 2026 CVSS 3.1 · 7.4 High EPSS < 1% KEV · Not listed
Description
A flaw was found in libslirp in icmp_forward_error(). When building an ICMP error response, the length of the quoted original IPv4 packet was taken from the IP header without clamping it to the actual buffer length. A truncated or malformed packet could cause an out-of-bounds heap read, leaking host memory into the ICMP error packet returned to a guest or container.

Remediation

Vendor 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. --- CME Mitigation Guidance (2026-11-04) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure. The highest-value action is to clamp quoted IPv4 payload length to actual buffer bounds in libslirp icmp_forward_error before copying data into ICMP error responses: upgrade to the corresponding fixed Red Hat builds, which clamp s_ip_len to the source buffer length msrc->m_len before copying payload data into the ICMP error packet, closing crafted truncated IPv4 packets with ip_len exceeding mbuf length. Until patched, this is a concern on guests or containers transmitting network traffic through libslirp, so restrict untrusted guests or containers from transmitting network traffic across libslirp virtual network interfaces. These controls limit blast radius and contain exploitation, but they do not fix the underlying out-of-bounds heap read defect — apply the upstream patch to fully remediate.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
cpe:/a:redhat:enterprise_linux:10
cpe:/a:redhat:enterprise_linux:8
cpe:/a:redhat:enterprise_linux:9
Type Values Removed Values Added
Description A flaw was found in libslirp in icmp_forward_error(). When building an ICMP error response, the length of the quoted original IPv4 packet was taken from the IP header without clamping it to the actual buffer length. A truncated or malformed packet could cause an out-of-bounds heap read, leaking host memory into the ICMP error packet returned to a guest or container.
Title Libslirp: libslirp: out-of-bounds heap read in icmp_forward_error() leading to information disclosure
First Time appeared Redhat
Redhat enterprise Linux
Redhat openshift
Weaknesses CWE-125
CPEs cpe:/a:redhat:openshift:4
cpe:/a:redhat:openshift:5
cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
Redhat openshift
References
Metrics cvssV3_1

{'score': 7.4, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Nov 9, 2026, 2:28 PM
Reserved
Nov 2, 2026, 11:39 PM
Status
Awaiting Analysis
Published
Nov 3, 2026, 12:17 AM
Modified
Nov 9, 2026, 3:17 PM
Severity
Important
Public date
Oct 30, 2026, 12:00 AM