CVE-2026-9539

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM 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
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0

A fix is available — apply it.

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(medium)
EG Risk
34(Track)
EG Risk 34/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
13%
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.

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibslirp0 (4.9.1-1ubuntu1.1) @ resolute2026-08-30ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
libslirp4.4.0-1 ... 4.9.3-1 (9 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
libslirp4.7.0-1 ... 4.9.4-1 (6 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
libslirp4.8.0-14.8.0-1+deb13u1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
libslirp4.8.0-1, 4.9.1-14.9.2-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 6× in last 7d / 59× 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.

Showing the most recent 100 of 192 total refreshes for this CVE.

  1. 2026-09-11 14:53 UTCEPSS rescore
  2. 2026-09-11 09:38 UTCEPSS rescore
  3. 2026-09-10 09:35 UTCEPSS rescore
  4. 2026-09-08 22:01 UTCEPSS rescore
  5. 2026-09-06 13:48 UTCEPSS rescore
  6. 2026-09-05 15:31 UTCEPSS rescore
  7. 2026-09-04 05:07 UTCEPSS rescore
  8. 2026-09-02 14:12 UTCEPSS rescore
  9. 2026-09-01 13:54 UTCEPSS rescore
  10. 2026-09-01 04:40 UTCEPSS rescore
  11. 2026-08-30 20:23 UTCEG score recompute
  12. 2026-08-30 20:23 UTCVendor advisory
  13. 2026-08-30 20:23 UTCGHSA enrichment
  14. 2026-08-30 19:18 UTCEPSS rescore
  15. 2026-08-30 01:22 UTCEPSS rescore
  16. 2026-08-28 21:42 UTCEPSS rescore
  17. 2026-08-27 14:25 UTCEPSS rescore
  18. 2026-08-26 14:47 UTCEPSS rescore
  19. 2026-08-25 13:49 UTCEPSS rescore
  20. 2026-08-24 14:18 UTCEPSS rescore
  21. 2026-08-24 13:53 UTCEG score recompute
  22. 2026-08-24 13:53 UTCVendor advisory
  23. 2026-08-24 13:53 UTCGHSA enrichment
  24. 2026-08-23 13:28 UTCEG score recompute
  25. 2026-08-23 13:28 UTCVendor advisory
Show 75 more
  1. 2026-08-23 13:28 UTCGHSA enrichment
  2. 2026-08-23 00:19 UTCEPSS rescore
  3. 2026-08-22 13:41 UTCEG score recompute
  4. 2026-08-22 13:41 UTCVendor advisory
  5. 2026-08-22 13:41 UTCGHSA enrichment
  6. 2026-08-21 23:49 UTCEPSS rescore
  7. 2026-08-21 07:19 UTCEG score recompute
  8. 2026-08-21 07:19 UTCVendor advisory
  9. 2026-08-21 07:19 UTCGHSA enrichment
  10. 2026-08-20 22:56 UTCEPSS rescore
  11. 2026-08-20 07:44 UTCVendor advisory
  12. 2026-08-20 07:44 UTCGHSA enrichment
  13. 2026-08-19 04:47 UTCEG score recompute
  14. 2026-08-19 04:47 UTCVendor advisory
  15. 2026-08-19 04:47 UTCGHSA enrichment
  16. 2026-08-17 13:47 UTCEPSS rescore
  17. 2026-08-16 20:48 UTCEG score recompute
  18. 2026-08-16 20:48 UTCVendor advisory
  19. 2026-08-16 20:48 UTCGHSA enrichment
  20. 2026-08-16 14:56 UTCEPSS rescore
  21. 2026-08-16 02:15 UTCEPSS rescore
  22. 2026-08-15 21:17 UTCEG score recompute
  23. 2026-08-15 21:17 UTCVendor advisory
  24. 2026-08-15 21:17 UTCGHSA enrichment
  25. 2026-08-15 01:31 UTCEPSS rescore
  26. 2026-08-14 21:44 UTCVendor advisory
  27. 2026-08-14 21:44 UTCGHSA enrichment
  28. 2026-08-13 22:13 UTCEG score recompute
  29. 2026-08-13 22:13 UTCVendor advisory
  30. 2026-08-13 22:13 UTCGHSA enrichment
  31. 2026-08-13 22:00 UTCEPSS rescore
  32. 2026-08-12 22:43 UTCEG score recompute
  33. 2026-08-12 22:43 UTCVendor advisory
  34. 2026-08-12 22:43 UTCGHSA enrichment
  35. 2026-08-12 13:51 UTCEPSS rescore
  36. 2026-08-11 23:12 UTCEG score recompute
  37. 2026-08-11 23:12 UTCVendor advisory
  38. 2026-08-11 23:12 UTCGHSA enrichment
  39. 2026-08-11 13:43 UTCEPSS rescore
  40. 2026-08-10 23:41 UTCVendor advisory
  41. 2026-08-10 23:41 UTCGHSA enrichment
  42. 2026-08-10 00:10 UTCEG score recompute
  43. 2026-08-10 00:10 UTCVendor advisory
  44. 2026-08-10 00:10 UTCGHSA enrichment
  45. 2026-08-09 13:47 UTCEPSS rescore
  46. 2026-08-09 00:39 UTCEG score recompute
  47. 2026-08-09 00:39 UTCVendor advisory
  48. 2026-08-09 00:39 UTCGHSA enrichment
  49. 2026-08-08 16:37 UTCEPSS rescore
  50. 2026-08-08 01:08 UTCEG score recompute
  51. 2026-08-08 01:08 UTCVendor advisory
  52. 2026-08-08 01:08 UTCGHSA enrichment
  53. 2026-08-07 16:30 UTCEPSS rescore
  54. 2026-08-07 01:37 UTCEG score recompute
  55. 2026-08-07 01:37 UTCVendor advisory
  56. 2026-08-07 01:37 UTCGHSA enrichment
  57. 2026-08-06 13:47 UTCEPSS rescore
  58. 2026-08-06 02:06 UTCEG score recompute
  59. 2026-08-06 02:06 UTCVendor advisory
  60. 2026-08-06 02:06 UTCGHSA enrichment
  61. 2026-08-05 19:17 UTCEPSS rescore
  62. 2026-08-05 02:36 UTCEG score recompute
  63. 2026-08-05 02:36 UTCVendor advisory
  64. 2026-08-05 02:36 UTCGHSA enrichment
  65. 2026-08-04 15:10 UTCEPSS rescore
  66. 2026-08-04 10:39 UTCEPSS rescore
  67. 2026-08-04 02:51 UTCEG score recompute
  68. 2026-08-04 02:51 UTCVendor advisory
  69. 2026-08-04 02:51 UTCGHSA enrichment
  70. 2026-08-03 10:36 UTCEPSS rescore
  71. 2026-08-03 03:16 UTCVendor advisory
  72. 2026-08-03 03:16 UTCGHSA enrichment
  73. 2026-08-02 03:45 UTCEG score recompute
  74. 2026-08-02 03:45 UTCVendor advisory
  75. 2026-08-02 03:44 UTCGHSA enrichment

Related CVEs(same vendor + same CWE)

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 0% probability of exploitation in the next 30 days, which ranks it in the top 87.4% of all scored CVEs.
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

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