HIGHpublic-safe

CVE-2026-66033

NVD: libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2_cipher_crypt() function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM... NVD: Attackers can exploit the underflow in the expression computing blocksize minus aadlen minus authentication tag length to trigger an out-of-bounds read and a memcpy call with a near-SIZE_MAX length argument, causing immediate process crash before any... OSV: libssh2 Integer Underflow DoS via AES-GCM Cipher Negotiation

CVSS
8.7 Severity
HIGH EPSS
0.0037 (30) KEV
-

Source-published summary

Possible impact

Source describes service availability risk. Possible impact: The affected service may become unavailable or unreliable.

Affected context

vendor/product: libssh2 / libssh2

Remediation / advisory

Patch confirmed by source text; fixed version context: commit.

Why it matters

Source describes service availability risk. Possible impact: The affected service may become unavailable or unreliable.; CVSS 8.7 (HIGH); EPSS percentile 30; not listed in KEV; Patch confirmed by source text; fixed version context: commit; sources: NVD, OSV.

What to verify

Confirm affected product/version, vendor advisory, patch or mitigation, and exposure.

Exposure hint

exposure unknown

Impact tags

service availability review

Urgency reasons

CVSS HIGHaffected product presentvendor advisory presentrecent updateremediation reference present

Source-derived note

Summary derived from NVD / OSV description; unsafe procedural detail is not shown.

Redaction metadata

source summary used: True
fallback summary used: False
unsafe procedural detail present: false
raw source displayed: false
public summary redacted: true

Remediation handoff

Public-safe static handoff for human/Codex remediation planning. Scan, patch, external execution, and auto remediation are disabled.

Handoff JSON Handoff Markdown Safe Codex prompt

Safety note

This radar shows source-published defensive context only. Exploit procedures, exploit strings, scanner commands, and auto-remediation are not provided.