CVE-2026-55200

HIGHNVD 8.38.3
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

This high-severity CVE scores 8.3 under NVD CVSS v3. EPSS exploit probability: 3.9% (90th percentile of EPSS-scored CVEs). GitHub Security Advisory CVSS 8.1 is lower than this score; a lower GitHub score revises it only when its advisory is newer than the CVE record's last change, and this advisory (published 2026-06-17) is not newer than that change (2026-10-22), so it does not.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 4 sources updated this weekElevated

Also known asEUVD-2026-37784 (ENISA EUVD) · GHSA-r8mh-x5qv-7gg2 (GitHub Security Advisories)Source: ENISA EUVD

8.3EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • Public exploit or proof-of-concept code is available
CISA-KEV: Not listedEPSS PROB: 3.9%CVSS: 8.3Exploit: Public PoCExposed services: Not assessed

A fix is available — apply it.

libssh2 1.11.1, fixed in commit 97acf3d, contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution.

CVSS v3
8.3
EG Score
8.3HIGHmedium confidence
EG Risk
53
EG Risk 53/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity83% × 45%
Impact severity (EG Severity): CVSS 8.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
3.9%
EPSS %ILE
90th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (8.3): severity, escalated by confirmed exploitation. This CVE's 8.3 is its impact severity (EG Severity), not escalated.

EG Severity
8.3 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
3.9% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-28). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track* at medium mission impactTrack at low, Track* at medium and Attend at high mission impact.CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

June 17, 2026

Last Modified

October 22, 2026

Advisory Details (5)

Auto-updated Jun 30, 2026
Patch available. Sources: github_commit, github_pr.
Web page

exploitarium/libssh2-cve-2026-55200-poc at main · bikini/exploitarium · GitHub

https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc
Web page

libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c | Advisories | VulnCheck

https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c
GitHub pull request

transport.c: Additional boundary checks for packet length

Fix merged in libssh2/libssh2 PR #2052 on 2026-06-12 — awaiting tagged release

https://github.com/libssh2/libssh2/pull/2052
GitHub commit

commit 97acf3dfda80 (libssh2/libssh2)

Fix landed in libssh2/libssh2 commit 97acf3dfda80 — awaiting tagged release

https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8
Web page

exploitarium/libssh2-cve-2026-55200-poc at main · bikini/exploitarium · GitHub

https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc

Patch Availability(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibssh2-1t64 (1.11.1-1ubuntu0.26.04.2) @ resolute2026-10-29ubuntu
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 13× in last 7d / 50× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 423 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 323 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-02 16:45 UTCEPSS rescoreEPSS 3.9% · 90th percentile
  2. 2026-11-01 16:34 UTCEPSS rescoreEPSS 3.9% · 90th percentile
  3. 2026-10-31 16:33 UTCEPSS rescoreEPSS 3.9% · 90th percentile
  4. 2026-10-30 16:34 UTCEPSS rescoreEPSS 3.9% · 90th percentile
  5. 2026-10-29 16:33 UTCEPSS rescoreEPSS 3.9% · 90th percentile
  6. 2026-10-29 16:26 UTCEG score recompute
  7. 2026-10-29 16:26 UTCVendor advisory
  8. 2026-10-29 16:26 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  9. 2026-10-28 16:32 UTCEPSS rescoreEPSS 3.9% · 90th percentile
  10. 2026-10-27 21:02 UTCEG score recompute
  11. 2026-10-27 21:02 UTCVendor advisory
  12. 2026-10-27 21:02 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  13. 2026-10-27 16:32 UTCEPSS rescoreEPSS 3.9% · 90th percentile
  14. 2026-10-26 16:31 UTCEPSS rescoreEPSS 3.9% · 90th percentile
  15. 2026-10-25 16:33 UTCEPSS rescoreEPSS 3.9% · 90th percentile
  16. 2026-10-25 14:19 UTCEG score recompute
  17. 2026-10-24 16:33 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  18. 2026-10-23 16:32 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  19. 2026-10-22 19:27 UTCVendor advisory
  20. 2026-10-22 19:27 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  21. 2026-10-22 18:42 UTCEG score recompute
  22. 2026-10-22 18:42 UTCVendor advisory
  23. 2026-10-22 18:41 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  24. 2026-10-22 16:34 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  25. 2026-10-21 16:33 UTCEPSS rescoreEPSS 4.0% · 90th percentile
Show 75 more
  1. 2026-10-20 16:33 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  2. 2026-10-19 16:32 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  3. 2026-10-18 16:32 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  4. 2026-10-18 03:30 UTCEG score recompute
  5. 2026-10-17 16:34 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  6. 2026-10-17 03:26 UTCEG score recompute
  7. 2026-10-17 03:26 UTCVendor advisory
  8. 2026-10-17 03:26 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  9. 2026-10-16 16:42 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  10. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  11. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  12. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  13. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  14. 2026-10-12 15:56 UTCEG score recompute
  15. 2026-10-11 19:39 UTCEG score recompute
  16. 2026-10-11 16:54 UTCEG score recompute
  17. 2026-10-11 14:17 UTCEG score recompute
  18. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  19. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  20. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  21. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  22. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  23. 2026-10-07 12:05 UTCOSV refresh
  24. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  25. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  26. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  27. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  28. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  29. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  30. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  31. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  32. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  33. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  34. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  35. 2026-09-23 17:54 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  36. 2026-09-20 20:16 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  37. 2026-09-18 19:28 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  38. 2026-09-17 19:31 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  39. 2026-09-17 18:16 UTCEG score recompute
  40. 2026-09-17 18:16 UTCVendor advisory
  41. 2026-09-17 18:16 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  42. 2026-09-16 14:08 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  43. 2026-09-16 05:15 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  44. 2026-09-15 03:11 UTCEPSS rescoreEPSS 4.0% · 90th percentile
  45. 2026-09-14 02:22 UTCEG score recompute
  46. 2026-09-14 02:22 UTCVendor advisory
  47. 2026-09-14 02:22 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  48. 2026-09-13 16:47 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  49. 2026-09-13 14:07 UTCEG score recompute
  50. 2026-09-13 14:07 UTCVendor advisory
  51. 2026-09-13 14:07 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  52. 2026-09-11 14:53 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  53. 2026-09-10 09:35 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  54. 2026-09-08 22:01 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  55. 2026-09-07 16:01 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  56. 2026-09-06 13:47 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  57. 2026-09-04 05:06 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  58. 2026-09-02 14:12 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  59. 2026-09-01 13:54 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  60. 2026-09-01 04:40 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  61. 2026-08-30 21:16 UTCEG score recompute
  62. 2026-08-30 21:16 UTCVendor advisory
  63. 2026-08-30 21:16 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  64. 2026-08-30 19:17 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  65. 2026-08-30 01:22 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  66. 2026-08-28 21:41 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  67. 2026-08-27 14:25 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  68. 2026-08-26 14:46 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  69. 2026-08-25 13:49 UTCEPSS rescoreEPSS 4.0% · 89th percentile
  70. 2026-08-24 22:22 UTCEG score recompute
  71. 2026-08-24 22:22 UTCVendor advisory
  72. 2026-08-24 22:22 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  73. 2026-08-24 05:18 UTCVendor advisory
  74. 2026-08-24 05:18 UTCGHSA enrichmentGHSA-r8mh-x5qv-7gg2 · GitHub severity CRITICAL · GitHub CVSS 8.1
  75. 2026-08-23 14:57 UTCVendor advisory

Publicly available exploits

(3 references)

Public exploit code is referenced for this CVE (3 GitHub PoCs). Defenders should treat patch urgency accordingly.

  • GitHub PoCxd20111/CVE-2026-55200
    Published Jun 29, 2026

    CVE-2026-55200 - Critical libssh2 Remote Code Execution Vulnerability

    Open source ↗
  • GitHub PoC0xBlackash/CVE-2026-55200
    Published Jun 23, 2026

    CVE-2026-55200

    Open source ↗
  • GitHub PoC0xredash/CVE-2026-55200
    Published Jun 23, 2026

    CVE-2026-55200

    Open source ↗

Frequently asked(5)

What is CVE-2026-55200?
CVE-2026-55200 is a high-severity vulnerability; its CVE record was published on June 17, 2026. libssh2 1.11.1, fixed in commit 97acf3d, contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve…
When was CVE-2026-55200 made public?
CVE-2026-55200 was made public on June 12, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on June 17, 2026. EchelonGraph's copy of the record carries a last-modified date of October 22, 2026; the record at its source may have been updated since.
Is CVE-2026-55200 actively exploited?
CVE-2026-55200 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 3.9% probability of exploitation in the next 30 days (90th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55200?
CVE-2026-55200 has a CVSS v3 base score of 8.3 (NVD).
How do I remediate CVE-2026-55200?
A fix for CVE-2026-55200 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55200 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-55200

Explore →

Is Your Infrastructure Affected by CVE-2026-55200?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.