CVE-2025-37921Public exploit

Lockdep warning via unlocked default FDB deletion

Published May 20, 2025 · Updated Aug 5, 2026

Improper locking in Linux kernel VXLAN VNI filtering allows local users to trigger a lockdep warning during VNI deletion. The vxlan_vni_delete_group path deletes the default remote's FDB entry without holding the VXLAN FDB hash lock around the lookup and removal. Reachability requires vnifilter mode, an external VXLAN device, a configured default remote, and permission to modify network links.

CVSS severity7.8
High
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper locking in Linux kernel VXLAN VNI filtering allows local users to trigger a lockdep warning during VNI deletion. The vxlan_vni_delete_group path deletes the default remote's FDB entry without holding the VXLAN FDB hash lock around the lookup and removal. Reachability requires vnifilter mode, an external VXLAN device, a configured default remote, and permission to modify network links.

The record

CVE
CVE-2025-37921
Published
May 20, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 20, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.18
  2. Affected versionversion=f9c4bb0b245cee35ef66f75bf409c9573d934cf9 <087a9eb9e5978e3ba362e1163691e41097e8ca20
  3. Affected versionversion=f9c4bb0b245cee35ef66f75bf409c9573d934cf9 <2d4a121296aa3940d2df9906f955c2b6b4e38bc3
  4. Affected versionversion=f9c4bb0b245cee35ef66f75bf409c9573d934cf9 <3576e9a80b6c4381b01ce0cbaa07f5e92d4492ed
  5. Affected versionversion=f9c4bb0b245cee35ef66f75bf409c9573d934cf9 <470206205588559e60035fceb5f256640cb45f99
  6. Affected versionversion=f9c4bb0b245cee35ef66f75bf409c9573d934cf9 <5cb9e07f84e527974b12e82e2549fa6c0cc6eef0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.18; version=f9c4bb0b245cee35ef66f75bf409c9573d934cf9 <087a9eb9e5978e3ba362e1163691e41097e8ca20; version=f9c4bb0b245cee35ef66f75bf409c9573d934cf9 <2d4a121296aa3940d2df9906f955c2b6b4e38bc3; version=f9c4bb0b245cee35ef66f75bf409c9573d934cf9 <3576e9a80b6c4381b01ce0cbaa07f5e92d4492ed; version=f9c4bb0b245cee35ef66f75bf409c9573d934cf9 <470206205588559e60035fceb5f256640cb45f99; version=f9c4bb0b245cee35ef66f75bf409c9573d934cf9 <5cb9e07f84e527974b12e82e2549fa6c0cc6eef0

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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