CVE-2026-66033

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: 1%CVSS: 7.5Exploit: None knownExposed: 0

A fix is available — apply it.

libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2_cipher_crypt() function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit the underflow in the expression computing blocksize minus aadlen minus authentication tag length to trigger an out-of-bounds read and a memcpy call with a near-SIZE_MAX length argument, causing immediate process crash before any authentication occurs.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
46%
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 Integer Underflow DoS via AES-GCM Cipher Negotiation | Advisories | VulnCheck

https://www.vulncheck.com/advisories/libssh2-integer-underflow-dos-via-aes-gcm-cipher-negotiation
github_pr

openssl: fix potential OOB read/write with AES-GCM in `ssh2_cipher_crypt()`

Upstream fix in progress (PR #2401 · libssh2/libssh2, state=closed)

https://github.com/libssh2/libssh2/pull/2401
github_commit

commit a2ed82d40964 (libssh2/libssh2)

Fix landed in libssh2/libssh2 commit a2ed82d40964 — awaiting tagged release

https://github.com/libssh2/libssh2/commit/a2ed82d40964bbc0d64cd717aa0a5a892117d2e6

Vendor Advisories for CVE-2026-66033(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-1.11.1-10.2.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(2)

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 / 139× 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 285 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-66033?
CVE-2026-66033 is a high vulnerability published on July 24, 2026. libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2ciphercrypt() function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit…
When was CVE-2026-66033 disclosed?
CVE-2026-66033 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-2026-66033 actively exploited?
CVE-2026-66033 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 54.0% of all scored CVEs.
What is the CVSS score of CVE-2026-66033?
CVE-2026-66033 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-66033?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66033, 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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