Vulnerability · Published Oct 21, 2026 · Assigned by CPANSec
CVE-2026-94140Rex versions through 1.16.1 for Perl accept an unknown SSH host key for remote rsync transfers because sync hardcodes StrictHostKeyChecking=no
Critical 9.1
In plain English
A critical-severity security flaw in Rex. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 37% of all known vulnerabilities).
Official description
Rex versions through 1.16.1 for Perl accept an unknown SSH host key for remote rsync transfers because sync hardcodes StrictHostKeyChecking=no. Every remote branch of sync builds its ssh command with that option, for password authentication, for private-key authentication and for the fallback. The ssh options a caller sets through set_openssh_opt reach the OpenSSH transport but not this command, so there is no configuration that restores host key checking for the transfer. An attacker who can redirect the connection before the real host key is known presents their own and the transfer proceeds: under password authentication sync sends the connection password to that server, an upload writes the selected local files to it, and a download writes what it returns to the local destination.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | rex | no fix listed | DEBIAN-CVE-2026-94140 |
| Debian:13 | rex | no fix listed | DEBIAN-CVE-2026-94140 |
| Debian:14 | rex | no fix listed | DEBIAN-CVE-2026-94140 |
| Ubuntu:22.04:LTS | rex | no fix listed | UBUNTU-CVE-2026-94140 |
| Ubuntu:24.04:LTS | rex | no fix listed | UBUNTU-CVE-2026-94140 |
| Ubuntu:26.04:LTS | rex | no fix listed | UBUNTU-CVE-2026-94140 |
| Ubuntu:26.10 | rex | no fix listed | UBUNTU-CVE-2026-94140 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Rex | 0 – through 1.16.1 |
Weakness: CWE-322 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N