Dragonfly is an open source P2P-based file distribution and image acceleration system. Prior to 2.1.0, the processPieceFromSource method does not update the structure’s usedTraffic field, because an uninitialized variable n is used as a guard to the AddTraffic method call, instead of the result.Size variable. A task is processed by a peer. The usedTraffic metadata is not updated during the processing. Rate limiting is incorrectly applied, leading to a denial-of-service condition for the peer. This vulnerability is fixed in 2.1.0.

Affected: Go: github.com/dragonflyoss/dragonfly, Go: d7y.io/dragonfly/v2

### Impact The processPieceFromSource method (figure 4.1) is part of a task processing mechanism. The method writes pieces of data to storage, updating a Task structure along the way. The method does not update the structure’s usedTraffic field, because an uninitialized variable n is used as a guard to the AddTraffic method call, instead of the result.Size variable.

```golang var n int64 result.Size, err = pt.GetStorage().WritePiece([skipped]) result.FinishTime = time.Now().UnixNano() if n > 0 { pt.AddTraffic(uint64(n)) } ```

A task is processed by a peer. The usedTraffic metadata is not updated during the processing. Rate limiting is incorrectly applied, leading to a denial-of-service condition for the peer.

### Patches

- Dragonfy v2.1.0 and above.

### Workarounds

There are no effective workarounds, beyond upgrading.

### References

A third party security audit was performed by Trail of Bits, you can see the [full report](https://github.com/dragonflyoss/dragonfly/blob/main/docs/security/dragonfly-comprehensive-report-2023.pdf).

If you have any questions or comments about this advisory, please email us at [dragonfly-maintainers@googlegroups.com](mailto:dragonfly-maintainers@googlegroups.com).

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