Software which sets SO_REUSEPORT_LB on a socket and then connects it to a host will not directly observe any problems. However, due to its membership in a load-balancing group, that socket will receive packets originating from any host. This breaks the contract of the connect(2) and implied connect via sendto(2), and may leave the application vulnerable to spoofing attacks.




The kernel failed to check the connection state of sockets when adding them to load-balancing groups. Furthermore, when looking up the destination socket for an incoming packet, the kernel will match a socket belonging to a load-balancing group even if it is connected, in violation of the contract that connected sockets are only supposed to receive packets originating from the connected host.
Advisories

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Fixes

Solution

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Workaround

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History

Wed, 22 Oct 2025 20:15:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 5.4, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 22 Oct 2025 18:00:00 +0000

Type Values Removed Values Added
Description Software which sets SO_REUSEPORT_LB on a socket and then connects it to a host will not directly observe any problems. However, due to its membership in a load-balancing group, that socket will receive packets originating from any host. This breaks the contract of the connect(2) and implied connect via sendto(2), and may leave the application vulnerable to spoofing attacks. The kernel failed to check the connection state of sockets when adding them to load-balancing groups. Furthermore, when looking up the destination socket for an incoming packet, the kernel will match a socket belonging to a load-balancing group even if it is connected, in violation of the contract that connected sockets are only supposed to receive packets originating from the connected host.
Title SO_REUSEPORT_LB breaks connect(2) for UDP sockets
Weaknesses CWE-488
References

cve-icon MITRE

Status: PUBLISHED

Assigner: freebsd

Published:

Updated: 2025-10-22T20:01:34.413Z

Reserved: 2025-01-29T03:07:26.190Z

Link: CVE-2025-24934

cve-icon Vulnrichment

Updated: 2025-10-22T19:58:36.275Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-10-22T18:15:34.013

Modified: 2025-10-22T21:12:32.330

Link: CVE-2025-24934

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.