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
59%
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) @ resolute2026-09-14ubuntu
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 12× in last 7d / 50× 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 290 total refreshes for this CVE.

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

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 41.3% 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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