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
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.9%CVSS: 7.5Exploit: None knownExposed services: Not assessed

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
7.5HIGHmedium confidence
EG Risk
34
EG Risk 34/100

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%
EPSS PROB
0.9%
EPSS %ILE
59th
KEV
Not listed

Published

June 17, 2026

Last Modified

July 14, 2026

Advisory Details (3)

Auto-updated Jun 17, 2026
Patch available. 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 / EcosystemFix (by version range) / 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 rangeFix by version rangeDependents
libssh2—
  • every version up to 1.11.1-r3: fixed in 1.11.1-r3
—
rust—
  • every version up to 1.96.1-r0: fixed in 1.96.1-r0
—
Alpine:v3.21(1)
PackageVulnerable rangeFix by version rangeDependents
libssh2—
  • every version up to 1.11.1-r2: fixed in 1.11.1-r2
—
Alpine:v3.22(1)
PackageVulnerable rangeFix by version rangeDependents
libssh2—
  • every version up to 1.11.1-r2: fixed in 1.11.1-r2
—
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
libssh2—
  • every version up to 1.11.1-r3: fixed in 1.11.1-r3
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
libssh21.11.1-1
  • every version up to 1.11.1-1+deb13u1: fixed in 1.11.1-1+deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
libssh21.11.1-1, 1.11.1-2, 1.11.1-3
  • every version up to 1.11.1-4: fixed in 1.11.1-4
—

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 7× in last 7d / 32× 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 309 total refreshes for this CVE.

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

Related CVEs(same product + same vendor + same CWE)

Same vendor

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redhat:RHSA-2026:29950 · ubuntu:USN-8486-1

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 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 0.9% probability of exploitation in the next 30 days (59th percentile of EPSS-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?
A fix for CVE-2026-55199 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55199 are linked in the Vendor Advisories panel on this page.

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