CVE-2026-55199

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.9%, top 42% of all CVEs by exploit prediction. GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: epss, ghsa, nvd
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 1762685, contains a pre-authentication denial of service vulnerability in the SSH_MSG_EXT_INFO handler in src/packet.c that allows a malicious SSH server to cause a client CPU exhaustion loop by sending a crafted extension count value. A malicious server can set nr_extensions to 0xFFFFFFFF during key exchange, causing the client to spin in a tight CPU loop for over 60 seconds because return values from _libssh2_get_string() are unchecked and the session timeout does not apply to CPU-bound loops.

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%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
58%
KEV
Not listed

Published

June 17, 2026

Last Modified

July 14, 2026

Advisory Details (3)

Auto-updated Jun 17, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit, github_pr.
generic

libssh2 - Pre-Authentication DoS via SSH_MSG_EXT_INFO Handler | Advisories | VulnCheck

https://www.vulncheck.com/advisories/libssh2-pre-authentication-dos-via-ssh-msg-ext-info-handler
github_pr

packet.c: check _libssh2_get_string() return in EXT_INFO handler

Upstream fix in progress (PR #1864 · libssh2/libssh2, state=closed)

https://github.com/libssh2/libssh2/pull/1864
github_commit

commit 17626857d20b (libssh2/libssh2)

Fix landed in libssh2/libssh2 commit 17626857d20b — awaiting tagged release

https://github.com/libssh2/libssh2/commit/17626857d20b3c9a1addfa45979dadcee1cd84a4

Vendor Advisories for CVE-2026-55199(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 (1.11.1-1ubuntu0.26.04.2) @ resolute2026-08-24ubuntu
redhatlibssh2-main-1.11.1-8.hum12026-06-25redhat

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

(7 across 6 ecosystems)
Alpine:v3.24(2)
PackageVulnerable rangeFixed inDependents
libssh2—1.11.1-r3—
rust—1.96.1-r0—
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
libssh2—1.11.1-r2—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
libssh2—1.11.1-r2—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
libssh2—1.11.1-r3—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
libssh21.11.1-11.11.1-1+deb13u1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
libssh21.11.1-1, 1.11.1-2, 1.11.1-31.11.1-4—

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 25× in last 7d / 142× 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 261 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-55199?
CVE-2026-55199 is a high vulnerability published on June 17, 2026. libssh2 through 1.11.1, fixed in commit 1762685, contains a pre-authentication denial of service vulnerability in the SSHMSGEXTINFO handler in src/packet.c that allows a malicious SSH server to cause a client CPU exhaustion loop by sending a crafted extension count value. A malicious server can set…
When was CVE-2026-55199 disclosed?
CVE-2026-55199 was first published in the National Vulnerability Database on June 17, 2026, with the most recent update on July 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55199 actively exploited?
CVE-2026-55199 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 42.4% of all scored CVEs.
What is the CVSS score of CVE-2026-55199?
CVE-2026-55199 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-55199?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55199, 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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