MosaicML Composer permits remote attackers to execute arbitrary code on affected installations by deserializing untrusted data. The flaw lies in the checkpoint parsing logic, where inputs are not properly validated, allowing a malicious payload to be executed in the context of the current process. This vulnerability is a classic insecure deserialization flaw, identified by CWE-502.

The affected product is MosaicML:Composer. No specific affected versions are listed; users should verify the version in use against the official release notes for a patch or fix.

The CVSS score of 7.8 indicates a high severity potential. The EPSS score is not available, and the vulnerability is not listed in the CISA KEV catalog. Exploitation requires user interaction: the target must visit a malicious page or open a malicious file, after which the insecure deserialization can be triggered. Once executed, the attacker gains code execution privileges within the composer process, potentially compromising the entire host. Given the lack of automatic exploitation, the risk is contingent on the attacker’s ability to lure a user to an untrusted checkpoint or page.