CVE-2021-35938

A symbolic link issue was found in rpm. It occurs when rpm sets the desired permissions and credentials after installing a file. A local unprivileged user could use this flaw to exchange the original file with a symbolic link to a security-critical file and escalate their privileges on the system. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

Weakness

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Affected Software

Potential Mitigations

• Follow the principle of least privilege when assigning access rights to entities in a software system.
• Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/132.html
• https://cwe.mitre.org/data/definitions/17.html
• https://cwe.mitre.org/data/definitions/35.html
• https://cwe.mitre.org/data/definitions/76.html

References

• https://access.redhat.com/security/cve/CVE-2021-35938
• https://bugzilla.redhat.com/show_bug.cgi?id=1964114
• https://bugzilla.suse.com/show_bug.cgi?id=1157880
• https://github.com/rpm-software-management/rpm/commit/25a435e90844ea98fe5eb7bef22c1aecf3a9c033
• https://github.com/rpm-software-management/rpm/pull/1919
• https://rpm.org/wiki/Releases/4.18.0
• https://security.gentoo.org/glsa/202210-22