A vulnerability has been identified within Rancher Manager, where using self-signed CA certificates and passing the -skip-verify flag to the Rancher CLI login command without also passing the –cacert flag results in the CLI attempting to fetch CA certificates stored in Rancher’s setting cacerts. This does not apply to any other commands and only applies to the login command if the –cacert flag was not provided.
An attacker with network-level access between the Rancher CLI and Rancher Manager could interfere with the TLS handshake to return a CA they control, despite the use of the --skip-verify flag. This may be abused to bypass TLS as a security control. Attackers can also see basic authentication headers in a Man-in-the-Middle due to the lack of TLS enforcement.
Please consult the associated MITRE ATT&CK - Technique - Man-in-the-Middle for further information about this category of attack.
This vulnerability is addressed by removing the ability to fetch CA certificates stored in Rancher’s setting cacerts when using the login command. Whenever required, for example when using self-signed certificates, CA certificates have to be explicitly passed with the –cacert flag.
Patched versions of Rancher include releases v2.13.2, v2.12.6, v2.11.10, and v2.10.11.
If a projecct can't upgrade to a fixed version, please make sure whenever required, for example when using self-signed certificates, to always explicitly pass CA certificates with the –cacert flag when using the login command.
If there are any questions or comments about this advisory:
0.0.0-20260129092249-bb0625fd18962.10.112.11.102.12.62.13.2Exploitability
AV:NAC:HPR:NUI:RScope
S:CImpact
C:HI:HA:H8.3/CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H