Is CVE-2026-9539 in the CISA KEV catalog?

No. CVE-2026-9539 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-9539?

CVE-2026-9539 has a CVSS v3 base score of 6.5 (Moderate).

What is the EPSS score for CVE-2026-9539?

CVE-2026-9539 has an EPSS score of 0.11% (1th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-9539?

Upgrade libslirp on debian unstable to 4.9.2-1 or later.

CVE & CISA-KEV Catalog

CVE-2026-9539

MEDIUM

6.5

CVSS v3

NVD

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).

CWE-125Out-of-bounds Read

How to fix

Remediation Available

libslirpDebian

Fixed in:4.9.2-1CVE-2026-9539

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeChanged

Impact

ConfidentialityHigh

IntegrityNone

AvailabilityNone

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

Exploit Intelligence

0.11%probability of exploitation in 30 days

1stpercentile

Low risk: more likely to be exploited than 1% of all known CVEs.

References

Other references3

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-25.