CVE-2026-66034

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-07-24. the CNA's CVSS baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:vulncheck, epss, ghsa
Trending — Patch released 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: 0%CVSS: 7.5Exploit: None knownExposed: 0

A fix is available — apply it.

libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1 response parser reads a server-controlled comment_len value and advances the parse pointer without verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup path frees an uninitialized pointer from a non-zeroed realloc() region.

CVSS v3
7.5
EG Score
7.5(high)
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%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
17%
KEV
Not listed

Published

July 24, 2026

Last Modified

July 28, 2026

Advisory Details (3)

Auto-updated Jul 24, 2026
Upstream fix merged — awaiting tagged release. Sources: github_pr, github_commit.
generic

libssh2 Heap Out-of-Bounds Read via publickey subsystem | Advisories | VulnCheck

https://www.vulncheck.com/advisories/libssh2-heap-out-of-bounds-read-via-publickey-subsystem
github_commit

commit a13bb6c773f0 (libssh2/libssh2)

Fix landed in libssh2/libssh2 commit a13bb6c773f0 — awaiting tagged release

https://github.com/libssh2/libssh2/commit/a13bb6c773f0d55ad1628cede57e99803cd898d9
github_pr

publickey: fix potential OOB read in `libssh2_publickey_list_fetch()`

Upstream fix in progress (PR #2202 · libssh2/libssh2, state=closed)

https://github.com/libssh2/libssh2/pull/2202

Vendor Advisories for CVE-2026-66034(3)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
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.

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 19× in last 7d / 19× 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.

  1. 2026-07-28 01:30 UTCVendor advisory
  2. 2026-07-28 01:30 UTCGHSA enrichment
  3. 2026-07-28 00:44 UTCEG score recompute
  4. 2026-07-28 00:44 UTCVendor advisory
  5. 2026-07-28 00:44 UTCGHSA enrichment
  6. 2026-07-27 14:14 UTCEPSS rescore
  7. 2026-07-27 13:17 UTCGHSA enrichment
  8. 2026-07-27 01:50 UTCEG score recompute
  9. 2026-07-27 01:49 UTCGHSA enrichment
  10. 2026-07-26 14:54 UTCEPSS rescore
  11. 2026-07-26 14:54 UTCEPSS rescore
  12. 2026-07-26 14:23 UTCEG score recompute
  13. 2026-07-26 14:23 UTCGHSA enrichment
  14. 2026-07-26 02:56 UTCEG score recompute
  15. 2026-07-26 02:55 UTCGHSA enrichment
  16. 2026-07-25 14:18 UTCEPSS rescore
  17. 2026-07-25 14:18 UTCEPSS rescore
  18. 2026-07-24 16:53 UTCEG score recompute
  19. 2026-07-24 16:52 UTCMITRE cvelistV5first tracked

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-66034?
CVE-2026-66034 is a high vulnerability published on July 24, 2026. libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an uninitialized pointer via the publickey subsystem. In libssh2publickeylistfetch(), the version 1…
When was CVE-2026-66034 disclosed?
CVE-2026-66034 was first published in the National Vulnerability Database on July 24, 2026, with the most recent update on July 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66034 actively exploited?
CVE-2026-66034 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 83.1% of all scored CVEs.
What is the CVSS score of CVE-2026-66034?
CVE-2026-66034 has a CVSS v4.0 base score of 7.5 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-66034?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66034, 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

Explore the affected products and dependency analysis for CVE-2026-66034

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