SO_REUSEPORT_LB breaks connect(2) for UDP sockets

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Summary

CVECVE-2025-24934
StatePUBLISHED
Assignerfreebsd
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-10-22 18:15:34 UTC
Updated2026-04-24 00:16:26 UTC
DescriptionSoftware 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.

Risk And Classification

Primary CVSS: v3.1 5.4 MEDIUM from ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Problem Types: CWE-488 | CWE-488 CWE-488: Exposure of Data Element to Wrong Session

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA FreeBSD FreeBSD affected 15.0-BETA2 p1 beta Not specified
CNA FreeBSD FreeBSD affected 14.3-RELEASE p5 release Not specified
CNA FreeBSD FreeBSD affected 13.5-RELEASE p6 release Not specified

References

ReferenceSourceLinkTags
security.freebsd.org/advisories/FreeBSD-SA-25:09.netinet.asc [email protected] security.freebsd.org
www.usenix.org/system/files/conference/usenixsecurity26/sec26_prepub_ben-sim... [email protected] www.usenix.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: MSc. student Omer Ben Simhon from the Hebrew University School of Computer Science and Engineering (en)

CNA: Prof. Amit Klein from the Hebrew University School of Computer Science and Engineering (en)

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