CVE-2026-9539

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory published 2026-06-24. a secondary CVSS source baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
6.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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).

CVSS v3
6.5
EG Score
6.5(high)
EPSS
1.3%
KEV
Not listed

Published

June 24, 2026

Last Modified

June 25, 2026

Advisory Details (3)

Auto-updated Jun 24, 2026
🔬 Proof of concept available. No patch confirmed yet.
generic🟡 PoC Available

SECURITY] libslirp: TCP URG OOB heap read information leak (#93) · Issues · slirp / libslirp · GitLab

https://gitlab.freedesktop.org/slirp/libslirp/-/work_items/93
generic

v4.9.2 · slirp / libslirp · GitLab

https://gitlab.freedesktop.org/slirp/libslirp/-/releases/v4.9.2
generic

oob: cap urgent data count to what is actually available (927bca73) · Commits · slirp / libslirp · GitLab

https://gitlab.freedesktop.org/slirp/libslirp/-/commit/927bca7344e31fd58e2f7afaca784aad4400eb84

Vendor Advisories for CVE-2026-9539(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 25× in last 7d / 44× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-06 23:28 UTCEG score recompute
  2. 2026-07-06 23:28 UTCVendor advisory
  3. 2026-07-06 23:28 UTCGHSA enrichment
  4. 2026-07-06 16:27 UTCEPSS rescore
  5. 2026-07-05 23:57 UTCEG score recompute
  6. 2026-07-05 23:57 UTCVendor advisory
  7. 2026-07-05 23:57 UTCGHSA enrichment
  8. 2026-07-05 02:31 UTCEPSS rescore
  9. 2026-07-05 00:26 UTCEG score recompute
  10. 2026-07-05 00:26 UTCVendor advisory
  11. 2026-07-05 00:26 UTCGHSA enrichment
  12. 2026-07-04 06:31 UTCEPSS rescore
  13. 2026-07-04 00:50 UTCEG score recompute
  14. 2026-07-04 00:50 UTCVendor advisory
  15. 2026-07-04 00:50 UTCGHSA enrichment
  16. 2026-07-03 01:19 UTCEG score recompute
  17. 2026-07-03 01:19 UTCVendor advisory
  18. 2026-07-03 01:19 UTCGHSA enrichment
  19. 2026-07-02 01:46 UTCEG score recompute
  20. 2026-07-02 01:46 UTCVendor advisory
  21. 2026-07-02 01:46 UTCGHSA enrichment
  22. 2026-07-01 15:07 UTCEPSS rescore
  23. 2026-07-01 02:15 UTCEG score recompute
  24. 2026-07-01 02:15 UTCGHSA enrichment
  25. 2026-06-30 23:22 UTCEPSS rescore
Show 19 more
  1. 2026-06-30 02:44 UTCEG score recompute
  2. 2026-06-30 02:44 UTCGHSA enrichment
  3. 2026-06-29 03:13 UTCEG score recompute
  4. 2026-06-29 03:13 UTCGHSA enrichment
  5. 2026-06-28 14:07 UTCEPSS rescore
  6. 2026-06-28 04:56 UTCEPSS rescore
  7. 2026-06-28 03:42 UTCEG score recompute
  8. 2026-06-28 03:42 UTCGHSA enrichment
  9. 2026-06-27 04:10 UTCEG score recompute
  10. 2026-06-27 04:10 UTCGHSA enrichment
  11. 2026-06-27 03:08 UTCEPSS rescore
  12. 2026-06-26 04:38 UTCEG score recompute
  13. 2026-06-26 04:38 UTCGHSA enrichment
  14. 2026-06-25 13:50 UTCEPSS rescore
  15. 2026-06-25 05:06 UTCEG score recompute
  16. 2026-06-25 05:06 UTCGHSA enrichment
  17. 2026-06-24 14:05 UTCEPSS rescore
  18. 2026-06-24 05:32 UTCEG score recompute
  19. 2026-06-24 05:30 UTCNVD updatefirst tracked

Frequently asked(5)

What is CVE-2026-9539?
CVE-2026-9539 is a medium vulnerability published on June 24, 2026. 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 CAPNETRAW) to leak gigabytes of sensitive host-process heap…
When was CVE-2026-9539 disclosed?
CVE-2026-9539 was first published in the National Vulnerability Database on June 24, 2026, with the most recent update on June 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-9539 actively exploited?
CVE-2026-9539 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-9539?
CVE-2026-9539 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-9539?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-9539, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-9539

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