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Researchers say SSHole OpenSSH bug is being used against Linux hosts
BleepingComputer reported Monday that firms including GreyNoise and Previdian recorded in-the-wild use of the OpenSSH SSHole flaw (CVE-2026-123158) after a proof-of-concept appeared Nov. 5.
Security firms told BleepingComputer that attackers are using the OpenSSH flaw nicknamed SSHole (CVE-2026-123158) against Linux systems, with exploitation attempts starting Nov. 5, the day a proof-of-concept became public1.
The bug, disclosed last week by researcher Ozgun Kultekin, can let an attacker log into accounts whose password hash is set to an asterisk on some musl-based Linux systems, including Alpine Linux used in cloud and virtual environments1. An oversized password can make musl's hashing function return an asterisk on error, which OpenSSH then treats as a match for the stored value1.
Kultekin said exploitation needs specific authentication settings, does not hit accounts with valid password hashes, and can yield root where the account has passwordless administrative privileges1. Maintainers shipped a fix in OpenSSH 10.6p2 on Nov. 5; exploit code followed about four hours later1.
Finnish firm Defused said over the weekend it saw a small number of actors trying to use SSHole, not widespread activity1. GreyNoise said it recorded the first successful in-the-wild exploitation at 00:46 UTC on Nov. 7, about 40 hours after the patch, logging 16 successful chains from six source IP addresses on networks it protects, and said those cases are not representative of broader SSHole activity1.
In those cases, GreyNoise said, the actor ran system and container reconnaissance, queried cloud metadata services, tried to read password hashes and root SSH keys, and attempted to change SSH authorized_keys files1. One attacker obtained root and installed TAC Agent, a Python command-and-control implant aimed at tac.vpnla.org that never received a task, according to the report1.
GreyNoise said implant comments, logs, and errors were in Chinese and that a missing tool check might indicate automated operation1. Previdian reported 20 successful exploitation attempts from 13 attacker IPs in nine countries1. Offensive security firm watchTower said Nov. 6 it saw SSHole use tied to botnets and cryptomining1.
BleepingComputer said administrators should update OpenSSH or disable SSH password authentication on affected systems, and look for unexpected password logins to accounts whose /etc/shadow field is an asterisk, unauthorized SSH keys, and TAC Agent files or startup services1.
