CVE-2026-66033: libssh2 Integer Underflow DoS via AES-GCM Cipher Negotiation

Overview

Severity

High (CVSS 7.5)

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploit Status

Not Exploited

Patch Tuesday

2026-Jul

Released

2026-07-26

Last Updated

2026-09-07

EPSS Score

0.58% (percentile: 45.9%)

Affected Products (3)

Other

• 21559-17084
• 21500-17084
• 21752-17084

Security Updates (1)

• Security Update

Revision History

• 2026-07-26: Information published.
• 2026-07-27: Information published.
• 2026-08-07: Information published.
• 2026-08-25: Information published.
• 2026-09-07: Information published.