VulnerabilityPublished 20 May 2025Updated 5 Nov 2026

CVE-2025-37961: Linux kernel · ipvs: fix uninit-value for saddr in do_output_route4

Affects Linux kernelSource GCVE Database

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Not known to be exploited.

Data as of 5 Nov 2026, 22:02 UTC

Severity

Low

Rated Low by Threat Radar's AI analysis · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation evidence

Disclosed: evidence found.
CVE published 20 May 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Linux Linux	Affected 3.10.91 – 4.1.11 5 affected builds	Fixed in–

AI-suggested

A fix for this vulnerability has been implemented in the Linux kernel. Users and administrators should apply the official kernel updates that include this patch to resolve the uninitialized value usage in ipvs. Since this is a kernel-level fix, upgrading to a patched kernel version is the recommended mitigation.

Description

CVE-2025-37961 is a vulnerability in the Linux kernel's IP Virtual Server (ipvs) subsystem where an uninitialized value for the source address (saddr) in the do_output_route4 function could cause issues in route connection. The flaw was identified by syzbot and involves improper handling of the saddr argument, which should be ignored but was still read, potentially preventing route connection. The issue has been fixed by changing the argument to ret_saddr to avoid using an uninitialized value.

Impact

The impact is related to the potential failure to connect the route due to reading an uninitialized source address value in the IPVS kernel code. This could lead to network communication issues within the affected kernel versions. There is no indication of privilege escalation, remote code execution, or denial of service beyond route connection failures. No known exploits in the wild have been reported.

Summary

This vulnerability in the Linux kernel ipvs component involves the use of an uninitialized value for the saddr argument in the do_output_route4 function. The problem was reported by syzbot, which detected an uninitialized value usage in the kernel code path related to IPVS packet transmission. The root cause is that although the input saddr value should be ignored (as per a prior commit), the code still reads it, which can prevent establishing the route correctly. The fix replaces the saddr argument with ret_saddr to ensure a properly initialized value is used.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Nov 2026, 22:02 UTC

Technical details

References

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