Loop with Unreachable Exit Condition ('Infinite Loop') Affecting libssh2 package, versions <1.11.1-r2


Severity

Recommended
0.0
medium
0
10

Snyk's Security Team recommends NVD's CVSS assessment. Learn more

Threat Intelligence

EPSS
0.92% (57th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-ALPINE321-LIBSSH2-17431897
  • published24 Jun 2026
  • disclosed17 Jun 2026

Introduced: 17 Jun 2026

CVE-2026-55199  (opens in a new tab)
CWE-835  (opens in a new tab)

How to fix?

Upgrade Alpine:3.21 libssh2 to version 1.11.1-r2 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream libssh2 package and not the libssh2 package as distributed by Alpine. See How to fix? for Alpine:3.21 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1