GHSA-f962-qm93-mj4c
Coder's unbounded memory allocation in provisioner file upload allows authenticated denial of service
Details
### Summary
`NewDataBuilder` in `provisionersdk/proto/dataupload.go` allocated a byte slice using the client-supplied `FileSize` from a `DataUpload` message without an upper-bound check. Although the DRPC wire limit is 4 MiB, the `FileSize` value itself was unconstrained
### Impact
An authenticated user able to reach the provisioner daemon serve endpoint could send a roughly 50-byte message declaring a huge `FileSize` (for example 1 TiB), triggering an unrecoverable Go out-of-memory abort that terminates `coderd`. This is a single-message denial of service affecting the entire deployment.
### Patches
The fix validates `FileSize` against an upper bound (`MaxFileSize = 100 MiB`) before allocation.
The fix was backported to all supported release lines:
| Release line | Patched version | |---|---| | 2.34 | [v2.34.2](https://github.com/coder/coder/releases/tag/v2.34.2) | | 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) | | 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) | | 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/v2.29.17) |
### Workarounds
Restrict access to the provisioner daemon serve endpoint to trusted provisioner daemon service accounts.
### Resources
- Fix: #25710
### Credits
Coder would like to thank Anthropic's Security Team (ANT-2026-22442) for independently disclosing this issue!
Are you affected?
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Affected packages
2.34.0 Fixed in: 2.34.2 go get github.com/coder/coder/v2@v2.34.2 2.33.0 Fixed in: 2.33.8 go get github.com/coder/coder/v2@v2.33.8 2.30.0 Fixed in: 2.32.7 go get github.com/coder/coder/v2@v2.32.7 2.24.0 Fixed in: 2.29.17 go get github.com/coder/coder/v2@v2.29.17