conda-forge-webservices has an Unauthorized Artifact Modification Race Condition

Vulnerability Description

conda-forge-webservices is the web app deployed to run conda-forge admin commands and linting. In versions prior to 2025.4.10, a race condition vulnerability has been identified in the conda-forge-webservices component used within the shared build infrastructure. This vulnerability, categorized as a Time-of-Check to Time-of-Use (TOCTOU) issue, can be exploited to introduce unauthorized modifications to build artifacts stored in the cf-staging Anaconda channel. Exploitation may result in the unauthorized publication of malicious artifacts to the production conda-forge channel. The core vulnerability results from the absence of atomicity between the hash validation and the artifact copy operation. This gap allows an attacker, with access to the cf-staging token, to overwrite the validated artifact with a malicious version immediately after hash verification, but before the copy action is executed. As the cf-staging channel permits artifact overwrites, such an operation can be carried out using the anaconda upload --force command. This vulnerability is fixed in 2025.4.10.

References

• https://github.com/conda-forge/conda-forge-webservices/security/advisories/GHSA-28cx-74fp-g2g2
• https://github.com/conda-forge/conda-forge-webservices/commit/141ed27617068debd150956341551df3a5a3807d