Libmodulemd: libmodulemd: unbounded recursion when parsing nested xmd yaml

Overview

A flaw was found in libmodulemd. When parsing module metadata, the xmd field is converted into nested GVariant values through recursive YAML mapping and sequence helpers without a recursion-depth or node-count limit. An attacker who can supply crafted modulemd YAML with deeply nested xmd content can cause stack exhaustion or excessive resource consumption, resulting in a denial of service.

Affected

• libmodulemd (all versions)
• libmodulemd (all versions)
• libmodulemd (all versions)
• libmodulemd (all versions)
• openshift/ose-rhel-coreos-8 (all versions)
• openshift/ose-rhel-coreos-9 (all versions)

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Workarounds

Until a fix is available, avoid parsing untrusted modulemd documents that may contain attacker-controlled xmd data. If such input must be accepted, reject unusually deep or large xmd structures before handing them to libmodulemd, and isolate parsing in a process with strict stack, CPU, and memory limits.