A public proof-of-concept has been released for a critical flaw in libssh2 (CVE-2026-55200), the client-side SSH library embedded in curl, Git, PHP, backup agents, firmware updaters, and countless appliances. A malicious or compromised SSH server can send a crafted packet that corrupts memory on the connecting client, with no credentials or user interaction needed, potentially leading to code execution. Rated 9.2, the bug affects all versions through 1.11.1. The fix was merged into the source on June 12, but no tagged release exists yet, so distributions are backporting it. The hardest part is that libssh2 is often statically bundled, so package updates miss those copies entirely.
Group-IB and Flare disclosed PamDOORa, a new Linux backdoor for sale on the Russian-speaking Rehub cybercrime forum at $900 (down from $1,600). PamDOORa hijacks the Linux Pluggable Authentication Module (PAM) framework that handles SSH logins - so it intercepts every legitimate user's password as they authenticate, before any application-level logging fires. The backdoor injects a malicious pam_linux.so module into the authentication stack rather than replacing files. It also tampers with lastlog, btmp, utmp, and wtmp to erase attacker login traces - meaning incident response teams who SSH in to investigate will have their own credentials silently stolen. Group-IB notes the abuse method is not yet in MITRE ATT&CK.
TrustStrike Labs