CVE-2025-3864: Connection pool exhaustion in hackney

Severity: low (CVSS 2.3 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-05-28 · updated 2026-06-17
Weakness: CWE-772

Description

Hackney fails to properly release HTTP connections to the pool after handling 307 Temporary Redirect responses. Remote attackers can exploit this to exhaust connection pools, causing denial of service in applications using the library. Fix for this issue has been included in 1.24.0 release.

Affected products

hackney: before 1.24.0 — fixed in 1.24.0

How to fix

Upgrade to a fixed version: hackney 1.24.0. Check the vendor advisory for mitigations.

References

https://cert.pl/en/posts/2025/05/CVE-2025-3864/
https://github.com/benoitc/hackney/commit/8f13ddac50d1626f8b9a47a08bd599e4efe1773d
https://github.com/benoitc/hackney/issues/717

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