MosaicML Composer Deserialization of Untrusted Data Remote Code Execution Vulnerability
Vulnerability Details
This vulnerability allows remote attackers to execute arbitrary code on affected installations of MosaicML Composer. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.
The specific flaw exists within the parsing of checkpoints. The issue results from the lack of proper validation of user-supplied data, which can result in deserialization of untrusted data. An attacker can leverage this vulnerability to execute code in the context of the current process.
Additional Details
MosaicML has issued an update to correct this vulnerability. More details can be found at:
https://github.com/mosaicml/composer/commit/6405188805a0054b4551ec49e4919c54c971d0e8
Disclosure Timeline
- 2026-02-12 - Vulnerability reported to vendor
- 2026-06-24 - Coordinated public release of advisory
- 2026-06-24 - Advisory Updated
Credit
Michael DePlante (@izobashi) of TrendAI Zero Day Initiative
