Dashboard / CVE-2026-66033

CVE-2026-66033

HIGH
MEDIUM Priority: 0.05 BB Relevance: 78/100
Published: 2026-07-24 Modified: 2026-11-08 First seen: 2026-11-08 Status: active

Attack Surface

Network Low Complexity No Auth No Interaction

CVSS Vector Breakdown

AV: Network
AC: Low
PR: None
UI: None
S: X
AT: None
VC: None
VI: None
VA: High

Description

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 ciphers during handshake. 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 authentication occurs.

Weakness Classification (2)

Affected Software (1)

VendorProductVersion
libssh2 libssh2 < 1.11.1

References & Advisories (3)

Bug Bounty Relevance

78 / 100
✓ Network accessible
✓ No authentication
✓ Low complexity
✓ No user interaction

CVSS Score

8.7 / 10.0 v4.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS — Exploitation Probability

0.58%
Raw Score 0.005830
Percentile 48.4%
Date 2026-11-13

EPSS Trend

2026-11-13
0.00583
2026-11-12
0.00583
2026-11-10
0.00583
2026-11-09
0.00583
2026-11-08
0.00583

Intelligence Sources

nvd ref →

External Links