CVE-2026-66035

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-07-24. a secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: None knownExposed: 0

A fix is available — apply it.

libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packet_length smaller than the cipher's block size during Encrypt-then-MAC cipher negotiation. In the fullpacket() function in src/transport.c, the ETM path allocates a buffer of packet_length bytes but copies blocksize minus one bytes via memcpy, causing an overflow that on 32-bit glibc writes attacker-controlled bytes into an adjacent chunk's SIZE field, enabling tcache bin confusion, overlapping live objects, and function pointer overwrite during the session handshake before authentication.

CVSS v3
7.5
EG Score
7.5(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
Severity75% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
39%
KEV
Not listed

Published

July 24, 2026

Last Modified

July 30, 2026

Advisory Details (3)

Auto-updated Jul 24, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit, github_pr.
generic

libssh2 Heap Buffer Overflow via ETM Cipher Negotiation | Advisories | VulnCheck

https://www.vulncheck.com/advisories/libssh2-heap-buffer-overflow-via-etm-cipher-negotiation
github_pr

transport: fix potential heap overflow on ETM decrypt

Upstream fix in progress (PR #2198 · libssh2/libssh2, state=closed)

https://github.com/libssh2/libssh2/pull/2198
github_commit

commit 42e33d81577e (libssh2/libssh2)

Fix landed in libssh2/libssh2 commit 42e33d81577e — awaiting tagged release

https://github.com/libssh2/libssh2/commit/42e33d81577ed4b95d4b4f6f845e5ee8efe5eeb4

Vendor Advisories for CVE-2026-66035(3)

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

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibssh2-1t64 (1.11.1-1ubuntu0.26.04.4) @ resolute2026-09-15ubuntu
redhatlibssh2-main-1.11.1-10.3.hum12026-07-27redhat

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

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFixed inDependents
libssh21.10.0-3 ... 1.11.1-5 (15 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
libssh21.11.1-1 ... 1.11.1-6 (7 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
libssh21.11.1-1, 1.11.1-2, 1.11.1-3, 1.11.1-41.11.1-5—

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 30× in last 7d / 133× 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 270 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-66035?
CVE-2026-66035 is a high vulnerability published on July 24, 2026. libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packetlength smaller than the cipher's block size during Encrypt-then-MAC…
When was CVE-2026-66035 disclosed?
CVE-2026-66035 was first published in the National Vulnerability Database on July 24, 2026, with the most recent update on July 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66035 actively exploited?
CVE-2026-66035 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 60.5% of all scored CVEs.
What is the CVSS score of CVE-2026-66035?
CVE-2026-66035 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-66035?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66035, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-66035

Explore →

Is Your Infrastructure Affected by CVE-2026-66035?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs