Unchecked Input for Loop Condition Affecting libssh2 package, versions [0,]
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-CONAN-LIBSSH2-17660952
- published28 Jun 2026
- disclosed17 Jun 2026
- creditUnknown
Introduced: 17 Jun 2026
CVE-2026-55199 (opens in a new tab)How to fix?
A fix was pushed into the master branch but not yet published.
Overview
Affected versions of this package are vulnerable to Unchecked Input for Loop Condition in the SSH_MSG_EXT_INFO handler during the initial handshake process. An attacker can cause the client application to become unresponsive by sending a crafted extension count value that triggers an infinite CPU loop. This is achieved by a malicious SSH server setting the nr_extensions field to a large value, causing the client to spin in a tight loop and exhaust CPU resources.
Workaround
This vulnerability can be mitigated by ensuring clients only connect to trusted SSH servers and implementing outbound network access controls (egress filtering) to block connections to unknown or untrusted external hosts.