Dashboard / CVE-2026-55199

CVE-2026-55199

HIGH
MEDIUM Priority: 0.08 BB Relevance: 77/100
Published: 2026-06-17 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
AT: Present
VC: None
VI: None
VA: High

Description

libssh2 through 1.11.1, fixed in commit 1762685, contains a pre-authentication denial of service vulnerability in the SSH_MSG_EXT_INFO handler in src/packet.c that allows a malicious SSH server to cause a client CPU exhaustion loop by sending a crafted extension count value. A malicious server can set nr_extensions to 0xFFFFFFFF during key exchange, causing the client to spin in a tight CPU loop for over 60 seconds because return values from _libssh2_get_string() are unchecked and the session timeout does not apply to CPU-bound loops.

Weakness Classification (1)

Affected Software (1)

VendorProductVersion
libssh2 libssh2 0

References & Advisories (3)

Bug Bounty Relevance

77 / 100
✓ Network accessible
✓ No authentication
✓ Low complexity
✓ No user interaction

CVSS Score

8.2 / 10.0 v4.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

EPSS — Exploitation Probability

0.92%
Raw Score 0.009180
Percentile 60.8%
Date 2026-11-13

EPSS Trend

2026-11-13
0.00918
2026-11-12
0.00918
2026-11-10
0.00918
2026-11-09
0.00918
2026-11-08
0.00918

Intelligence Sources

mitre ref →

External Links