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Python EUVDEUVD-2025-28273

| CVE-2025-48945 HIGH
Use After Free (CWE-416)
2025-06-20 security-advisories@github.com GHSA-5qpg-rh4j-qp35
Use After Free Python Denial Of Service Red Hat Suse
8.2
CVSS 4.0 · GitHub Advisory
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Severity by source

GitHub Advisory PRIMARY
8.2 HIGH
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Ubuntu
MEDIUM
qualitative
SUSE
5.9 MEDIUM
AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H
Red Hat
5.5 MEDIUM
qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None

Lifecycle Timeline

4
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
EUVD ID Assigned
Mar 15, 2026 - 00:19 euvd
EUVD-2025-28273
Analysis Generated
Mar 15, 2026 - 00:19 vuln.today
CVE Published
Jun 20, 2025 - 20:15 nvd
HIGH 8.2

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 1 pypi packages depend on pycares (1 direct, 0 indirect)

Ecosystem-wide dependent count for version 4.9.0.

DescriptionGitHub Advisory

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.

AnalysisAI

pycares versions prior to 4.9.0 contain a use-after-free vulnerability (CWE-416) in the Channel object that crashes the Python interpreter when garbage collection occurs during pending DNS queries. This denial-of-service vulnerability affects any application using pycares for asynchronous DNS resolution; attackers can trigger interpreter crashes by manipulating DNS query timing, though no active exploitation or public POC is documented. The CVSS 8.2 score reflects high availability impact, but real-world exploitability is limited by the requirement for application-level DNS query patterns and Python garbage collection timing.

Technical ContextAI

pycares is a Python binding (CPE: pycares) that wraps c-ares (a C library for asynchronous DNS name resolution per RFC 1035). The vulnerability exists in the Channel class, which manages DNS queries asynchronously. When a Channel object is garbage collected while DNS queries remain pending, the underlying c-ares library structures are freed, but active query callbacks may still reference this freed memory—a classic use-after-free condition (CWE-416: Use After Free). This occurs at the memory safety boundary between Python's garbage-collected heap and c-ares' manually-managed C memory, where Python's reference counting may release the Channel before c-ares completes query cleanup. The fix in v4.9.0 implements safe channel destruction logic to ensure pending queries complete or are properly cancelled before memory is released.

RemediationAI

Upgrade pycares to version 4.9.0 or later; details: Applies safe channel destruction mechanism that ensures pending queries complete or are cancelled before memory release; verification: pip show pycares | grep Version (confirm 4.9.0+) Workaround (Temporary): Explicit Channel cleanup before application exit or scope end; details: Manually call channel.close() or use context managers to ensure Channel lifecycle is explicit; avoids reliance on Python garbage collection timing; code_example: with Channel() as ch: query(ch)

ensures cleanup

Mitigation: Monitor DNS query patterns and Python process stability; details: Implement health checks; if using pycares pre-4.9.0, track correlated interpreter crashes with DNS query bursts

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Same weakness CWE-416 – Use After Free

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Same technique Use After Free

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8.1

Vendor StatusVendor

Ubuntu

Priority: Medium
pycares
Release Status Version
bionic needs-triage -
focal needs-triage -
jammy needs-triage -
noble needs-triage -
upstream needs-triage -
plucky ignored end of life, was needs-triage
oracular ignored end of life, was needs-triage
questing needs-triage -

Debian

Bug #1109377
pycares
Release Status Fixed Version Urgency
bullseye vulnerable 3.1.1-1 -
bookworm vulnerable 4.3.0-2 -
trixie vulnerable 4.4.0-2 -
forky, sid fixed 5.0.1-3 -
(unstable) fixed 4.9.0-1 -

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise Desktop 15 SP6 SUSE Linux Enterprise High Performance Computing 15 SP6 SUSE Linux Enterprise Module for Python 3 15 SP6 SUSE Linux Enterprise Server 15 SP6 SUSE Linux Enterprise Server for SAP Applications 15 SP6 Fixed
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise High Performance Computing 15 SP7 SUSE Linux Enterprise Module for Python 3 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Fixed

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EUVD-2025-28273 vulnerability details – vuln.today
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