pycares is a Python module which provides an interface to c-ares. c-ares is a C library that performs DNS requests and name resolutions asynchronously. Prior to version 4.9.0, pycares is vulnerable to a use-after-free condition that occurs when a Channel object is garbage collected while DNS queries are still pending. This results in a fatal Python error and interpreter crash. The vulnerability has been fixed in pycares 4.9.0 by implementing a safe channel destruction mechanism.
Weakness
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Pycares | Ubuntu | oracular | * |
| Pycares | Ubuntu | plucky | * |
Potential Mitigations
References
- https://github.com/aio-libs/aiodns/commit/f259a6e3650555157af53ac2b39f2ff545321d55
- https://github.com/aio-libs/aiodns/releases/tag/v3.5.0
- https://github.com/saghul/pycares/commit/ebfd7d71eb8e74bc1057a361ea79a5906db510d4
- https://github.com/saghul/pycares/releases/tag/v4.9.0
- https://github.com/saghul/pycares/security/advisories/GHSA-5qpg-rh4j-qp35
- https://github.com/saghul/pycares/security/advisories/GHSA-5qpg-rh4j-qp35