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CVE-2026-9539

28
FAUCET Score

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).

First published: Jun 24, 2026Last modified: Jun 24, 2026

Impacted Technologies

VendorProductVersion(s)CPE
Freedesktop.OrgLibslirp
>= 0, < 4.9.2CNA affecteddefault unaffected

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
2.0
Impact Score
4.0
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.11%
Probability of exploitation in next 30 days
EPSS Percentile
1.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0011 is in the 8th percentile among its peer group of 15,938 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (5)

microsoftpatch availablevia msrc
Product: azl3 libslirp 4.7.0-1 on Azure Linux 3.0Fixed in: 4.9.3-1
microsoftpatch availablevia msrc
Product: 21469-17084Fixed in: 4.9.3-1
ubuntupatch availablevia ubuntu_usn
Product: libslirp (jammy)Fixed in: 4.6.1-1ubuntu0.2
ubuntupatch availablevia ubuntu_usn
Product: libslirp (noble)Fixed in: 4.7.0-1ubuntu3.1
ubuntupatch availablevia ubuntu_usn
Product: libslirp (resolute)Fixed in: 4.9.1-1ubuntu1.1

Vendor Advisories (2)

ubuntuUSN-8550-1

libslirp vulnerability

Jul 15, 2026
microsoft2026-Jun/CVE-2026-9539Moderate

libslirp TCP URG OOB Read Information Leak

Jun 9, 2026

References

gitlab.freedesktop.org / slirp/libslirp/-/commit/927bca7344e31fd58e2f7afaca784aad4400eb84
gitlab.freedesktop.org / slirp/libslirp/-/releases/v4.9.2
gitlab.freedesktop.org / slirp/libslirp/-/work_items/93