Executive brief
OpenSSH is a widely used tool for secure remote access and file transfers. A flaw in its internal SFTP server component causes it to ignore security settings if they are placed too far down in a long list of configuration commands. This could lead to a situation where intended security protections are not actually active, potentially allowing unauthorized file access or other security policy violations.
Technical details
A vulnerability exists in the 'internal-sftp' subsystem of OpenSSH's sshd where command-line arguments are silently truncated after the 9th argument. This is caused by improper validation of the specified quantity of input (CWE-1284). If an administrator configures the internal SFTP server with a long string of arguments where security-critical options (such as read-only mode or path restrictions) appear in the 10th position or later, those options will be discarded. An attacker could exploit this if the lack of these intended security properties allows for unauthorized actions on the SFTP server. This issue is resolved in OpenSSH version 10.4.
Affected products
- OpenBSD OpenSSH before 10.4
Timeline
- 2026-07-06: patched: OpenSSH 10.4 released with fix
- 2026-07-08: disclosed: CVE-2026-59997 published