pycares has a Use-After-Free Vulnerability
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-416 and the CVSS impact.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
- Fix · CNA aiodns (aio-libs) Fixed in 4.9.0
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
Not affected: 3 products
- Red Hat Ansible Automation Platform 2
- Red Hat Satellite 6
- Red Hat Update Infrastructure 4 for Cloud Providers
Timeline
- 2026-10-02 Threatist record created from CVE-2025-48945
References
Other 5
- https://github.com/saghul/pycares/security/advisories/GHSA-5qpg-rh4j-qp35
- https://github.com/aio-libs/aiodns/commit/f259a6e3650555157af53ac2b39f2ff545321d55
- https://github.com/saghul/pycares/commit/ebfd7d71eb8e74bc1057a361ea79a5906db510d4
- https://github.com/aio-libs/aiodns/releases/tag/v3.5.0
- https://github.com/saghul/pycares/releases/tag/v4.9.0
More aio-libs vulnerabilities
- TI-2025-38826 aiomysql allows arbitrary access to client files through vulnerability of a malicious MySQL server CVSS 4.0HIGH 8.2
- TI-2024-15436 aiohttp.web.static(follow_symlinks=True) is vulnerable to directory traversal CVSS 3.1HIGH 7.5
- TI-2023-25769 Request smuggling in aiohttp CVSS 3.1HIGH 7.5
- TI-2023-18906 aiohttp vulnerable to HTTP request smuggling CVSS 3.1HIGH 7.5
- TI-2023-26746 aiohttp's ClientSession is vulnerable to CRLF injection via version CVSS 3.1HIGH 7.2
- TI-2026-66145 Multidict: Reference leak in CIMultiDict/MultiDict items-view union and subtraction CVSS 3.1MEDIUM 5.3
Sources
- CVE-2025-48945 · CVE Program
- CVE-2025-48945 · NVD
- FIRST EPSS
- CVE-2025-48945 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences