Libslirp: libslirp: out-of-bounds heap read in icmp_forward_error() leading to information disclosure
Affects libslirp when it builds ICMP error replies for truncated or malformed packets. Red Hat lists RHEL 8, 9 and 10 and OpenShift Container Platform 4 and 5, but no fixed version is listed in the checked facts.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- No fix listed
- Who is exposed
- Not reported
Do first: Workaround: The checked facts do not list a workaround for the period before a fix is available. Until a fixed package is released, check the Red Hat advisory for any mitigation it gives.
- Exploitation?/40Exploitation: unknown (data gap). No CISA SSVC exploitation rating yet
- Exposure?/25Exposure: unknown (data gap). Advisories don't say whether default setups are affected
- Reach10/20Shipped in major Linux distributions
- Severity7.4/10CVSS 7.4
- No patch5/5No patch listed yet
What would change the score
- Would score about 77 if added to CISA KEV
- Would score about 72 if CISA's SSVC rates exploitation active
- Would score about 44 if advisories confirm default setups are exposed
CVE-2026-120830 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.4 (high) and affects Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 and 2 more; no fixed version is listed yet.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- FIRST's estimate of the chance attackers exploit it in the next 30 days, updated daily.What do these mean? →
- 0.22% · 12th percentile
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 22/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
libslirp, a user-mode networking library used by QEMU and other virtualization tools, is affected. A malformed or truncated packet can cause it to read memory beyond its allocated buffer, and the leaked host memory can be included in an ICMP error reply sent back to a guest virtual machine or container.
Read the original 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.
What to do
Workaround: The checked facts do not list a workaround for the period before a fix is available. Until a fixed package is released, check the Red Hat advisory for any mitigation it gives.
Timeline
- CVE published
- First seen by cve.now
- Record last updated
Affected versions
- libslirp
Version range not reported
- container-tools:rhel8/libslirp
Version range not reported
- libslirp
Version range not reported
- libslirp
Version range not reported
- openshift/ose-rhel-coreos-8
Version range not reported
- openshift/ose-rhel-coreos-9
Version range not reported
- openshift/ose-rhel-coreos-9
Version range not reported
Evidence 3
- Report
- Link
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-120830
Is CVE-2026-120830 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
The bug is an out-of-bounds heap read in icmp_forward_error(), the libslirp function that builds ICMP error replies. A truncated or malformed packet can make it read past its buffer, and the leaked host heap memory can end up in the ICMP error packet returned to a guest or container.Source: access.redhat.com
Am I affected, and how do I check?
Red Hat lists Red Hat Enterprise Linux 8, 9 and 10 and Red Hat OpenShift Container Platform 4 and 5, but the checked facts give no version ranges. To check a system, run rpm -q libslirp and compare the result with the package versions in the Red Hat advisory for this CVE.Source: access.redhat.com
How do I fix CVE-2026-120830?
The checked facts do not name a fixed version, so no upgrade target can be stated. Use the Red Hat advisory for CVE-2026-120830 to find the fixed libslirp package for each product.Source: access.redhat.com
What if there's no patch?
The checked facts do not list a workaround for the period before a fix is available. Until a fixed package is released, check the Red Hat advisory for any mitigation it gives.Source: access.redhat.com