CVE-2021-3864

A flaw was found in the way the dumpable flag setting was handled when certain SUID binaries executed its descendants. The prerequisite is a SUID binary that sets real UID equal to effective UID, and real GID equal to effective GID. The descendant will then have a dumpable value set to 1. As a result, if the descendant process crashes and core_pattern is set to a relative value, its core dump is stored in the current directory with uid:gid permissions. An unprivileged local user with eligible root SUID binary could use this flaw to place core dumps into root-owned directories, potentially resulting in escalation of privileges.

Weakness

The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.

Affected Software

Extended Description

Access control involves the use of several protection mechanisms such as:

When any mechanism is not applied or otherwise fails, attackers can compromise the security of the product by gaining privileges, reading sensitive information, executing commands, evading detection, etc. There are two distinct behaviors that can introduce access control weaknesses:

Potential Mitigations

• Compartmentalize the system to have “safe” areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
• Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/19.html
• https://cwe.mitre.org/data/definitions/441.html
• https://cwe.mitre.org/data/definitions/478.html
• https://cwe.mitre.org/data/definitions/479.html
• https://cwe.mitre.org/data/definitions/502.html
• https://cwe.mitre.org/data/definitions/503.html
• https://cwe.mitre.org/data/definitions/536.html
• https://cwe.mitre.org/data/definitions/546.html
• https://cwe.mitre.org/data/definitions/550.html
• https://cwe.mitre.org/data/definitions/551.html
• https://cwe.mitre.org/data/definitions/552.html
• https://cwe.mitre.org/data/definitions/556.html
• https://cwe.mitre.org/data/definitions/558.html
• https://cwe.mitre.org/data/definitions/562.html
• https://cwe.mitre.org/data/definitions/563.html
• https://cwe.mitre.org/data/definitions/564.html
• https://cwe.mitre.org/data/definitions/578.html

References

• https://access.redhat.com/security/cve/CVE-2021-3864
• https://bugzilla.redhat.com/show_bug.cgi?id=2015046
• https://lore.kernel.org/all/20211221021744.864115-1-longman%40redhat.com/
• https://lore.kernel.org/all/20211226150310.GA992%401wt.eu/
• https://lore.kernel.org/lkml/20211228170910.623156-1-wander%40redhat.com/
• https://security-tracker.debian.org/tracker/CVE-2021-3864
• https://www.openwall.com/lists/oss-security/2021/10/20/2
• https://access.redhat.com/security/cve/CVE-2021-3864
• https://bugzilla.redhat.com/show_bug.cgi?id=2015046
• https://lore.kernel.org/all/20211221021744.864115-1-longman%40redhat.com/
• https://lore.kernel.org/all/20211226150310.GA992%401wt.eu/
• https://lore.kernel.org/lkml/20211228170910.623156-1-wander%40redhat.com/
• https://security-tracker.debian.org/tracker/CVE-2021-3864
• https://www.openwall.com/lists/oss-security/2021/10/20/2