How severe is GHSA-5qpg-rh4j-qp35?

No CVSS score has been assigned to GHSA-5qpg-rh4j-qp35 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-5qpg-rh4j-qp35?

GHSA-5qpg-rh4j-qp35 affects the following packages: pycares (PyPI). Ecosystems affected: PyPI.

How do I fix GHSA-5qpg-rh4j-qp35?

Update pycares to 4.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5qpg-rh4j-qp35 is resolved across your whole dependency graph.

How do I detect GHSA-5qpg-rh4j-qp35 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pycares. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-5qpg-rh4j-qp35 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-5qpg-rh4j-qp35?

O3 pinpoints whether GHSA-5qpg-rh4j-qp35 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-5qpg-rh4j-qp35 actively exploited in the wild?

No public exploit code has been indexed for GHSA-5qpg-rh4j-qp35 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-5qpg-rh4j-qp35?

GHSA-5qpg-rh4j-qp35 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 31th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-5qpg-rh4j-qp35?

GHSA-5qpg-rh4j-qp35 is classified as Use After Free (CWE-416). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-5qpg-rh4j-qp35 published, and has it been updated?

GHSA-5qpg-rh4j-qp35 was published on June 16, 2025 and was last updated on October 16, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

GHSA-5qpg-rh4j-qp35

pycares has a Use-After-Free Vulnerability

Also known asCVE-2025-48945

Published

Jun 16, 2025

Updated

Oct 16, 2025

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk31th percentile-0.12%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

🐍pycares

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

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.

Details

Root Cause

The vulnerability stems from improper handling of callback references when the Channel object is destroyed:

When a DNS query is initiated, pycares stores a callback reference using ffi.new_handle()
If the Channel object is garbage collected while queries are pending, the callback references become invalid
When c-ares attempts to invoke the callback, it accesses freed memory, causing a fatal error

This issue was much more likely to occur when using event_thread=True but could happen without it under the right circumstances.

Technical Details

The core issue is a race condition between Python's garbage collector and c-ares's callback execution:

When __del__ is called from within a c-ares callback context, we cannot immediately call ares_destroy() because c-ares is still executing code after the callback returns
c-ares needs to execute cleanup code after our Python callback returns (specifically at lines 1422-1429 in ares_process.c)
If we destroy the channel too quickly, c-ares accesses freed memory

Impact

Applications using pycares can be crashed remotely by triggering DNS queries that result in Channel objects being garbage collected before query completion. This is particularly problematic in scenarios where:

Channel objects are created per-request
Multiple failed DNS queries are processed rapidly
The application doesn't properly manage Channel lifecycle

The error manifests as:

Fatal Python error: b_from_handle: ffi.from_handle() detected that the address passed points to garbage

Fix

The vulnerability has been fixed in pycares 4.9.0 by implementing a safe channel destruction mechanism

Mitigation

For Application Developers

Upgrade to pycares >= 4.9.0 - This version includes the fix and requires no code changes

Best practices (optional but recommended):

# Explicit cleanup
channel.close()

# Or use context manager
with pycares.Channel() as channel:
    # ... use channel ...
# Automatically closed

Avoid creating Channel objects per-request - Prefer long-lived instances for better performance and safety

The fix is completely transparent - no API changes or code modifications are required.

Credit

This vulnerability was reported by @vEpiphyte through the aio-libs security program.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`pycares`	all versions	4.9.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pycares. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update pycares to 4.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5qpg-rh4j-qp35 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-5qpg-rh4j-qp35 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-5qpg-rh4j-qp35. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## Summary 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. ## Details ### Root Cause The vulnerability stems from improper handling of callback references when the Channel object is destroyed: 1. When a DNS query is initiated, pycares stores a callback reference using `ffi.new_handle()` 2. If the Channel object is garbage collected while queries are pending, the callback references become invalid 3. When c-ares attempts to invoke the c

O3 Security · Impact-Aware SCA

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