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VulnerabilityPublished

CVE-2026-9539: freedesktop.org libslirp · Out-of-bounds Read

Affects freedesktop.org libslirpSource CVE Database V5

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Not known to be exploited · CVSS 6.5 Medium : upgrade to 4.9.2 when convenient.

Data as of 6 Nov 2026, 23:24 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 12% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 4.9.2
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    Public exploit code: GitHub proofs of concept

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), GitHub proofs of concept, the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

What to do

Upgrade freedesktop.org libslirp to 4.9.2.

Affected software

ProductAffectedFixed in
freedesktop.orglibslirpAffected
  • <4.9.2
Fixed in
  • 4.9.2

AI-suggested

If you cannot patch yet, restrict privileged access within guest VMs to trusted users only and monitor for unusual TCP urgent data usage patterns. Avoid running untrusted code with root or CAP_NET_RAW privileges inside guest VMs.

Description

An out-of-bounds heap read and integer underflow in the TCP urgent data handling (sosendoob) in freedesktop.org libslirp version before v4.9.2 on hypervisor host environments (e.g., QEMU) allows a privileged guest VM attacker (root or CAP_NET_RAW) to leak gigabytes of sensitive host-process heap memory via sending crafted TCP segments with manipulated URG flags and urgent pointers (ti_urp).

References

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