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
47%
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) @ resolute2026-09-18ubuntu
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 28× in last 7d / 129× 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 300 total refreshes for this CVE.

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

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 53.5% 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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