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.
CVE-2026-66034
HIGHPre-NVD 7.57.5
EchelonGraph scoreLOW confidence
This high-severity CVE scores 7.5 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: cna:vulncheck
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: —CVSS: 7.5Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 7.5(low)
- EG Risk
- 38(Track)EG Risk 38/100SSVC: 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 computedSeverity75% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS
- —
- KEV
- Not listed
Published
July 24, 2026
Last Modified
July 24, 2026
Advisory Details (3)
Auto-updated Jul 24, 2026Upstream 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-subsystemgithub_commit
commit a13bb6c773f0 (libssh2/libssh2)
Fix landed in libssh2/libssh2 commit a13bb6c773f0 — awaiting tagged release
https://github.com/libssh2/libssh2/commit/a13bb6c773f0d55ad1628cede57e99803cd898d9github_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/2202Vendor Advisories for CVE-2026-66034(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 2× in last 7d / 2× 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.
- 2026-07-24 16:53 UTCEG score recompute
- 2026-07-24 16:52 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Same CWE
10 shownCWE-125 · CWE-908
- CVE-2014-2896EG 9.8CRITICAL
- CVE-1999-0006EG 9.8EPSS 96%CRITICAL
- CVE-2014-1508EG 9.1EPSS 90%CRITICAL
- CVE-2014-0160NVD 7.5EG 9.0 KEVEPSS 100%HIGH
- CVE-2014-1497EG 8.8HIGH
- CVE-2011-3406EG 8.8EPSS 98%HIGH
- CVE-2008-3475EG 8.8EPSS 98%HIGH
- CVE-2008-4197EG 8.8EPSS 93%HIGH
- CVE-2008-2934EG 8.8HIGH
- CVE-1999-0029EG 8.4HIGH
Frequently asked(4)
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. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-66034?
CVE-2026-66034 has a CVSS v3 base score of 7.5 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
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
Is Your Infrastructure Affected by CVE-2026-66034?
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