CVE-2025-21826 | netfilter: nf_tables: reject mismatching sum of field_len with set key length

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: reject mismatching sum of field_len with set key length The field length description provides the length of each separated key field in the concatenation, each field gets rounded up to 32-bits to calculate the pipapo rule width from pipapo_init(). The set key length provides the total size of the key aligned to 32-bits. Register-based arithmetics still allows for combining mismatching set key length and field length description, eg. set key length 10 and field description [ 5, 4 ] leading to pipapo width of 12.

Published: 2025-03-06 Last update: 2026-05-12 Assigner: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Conclusion & alert: CVE-2025-21826 is rated Low Risk (26.2/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.04%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-21826

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-14 0.05% 0.04% -0.01%
2 2025-11-18 0.04% 0.05% +0.01%
3 2025-10-31 0.04%

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-21826

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
1.8 3.6 [email protected]

Weakness enumeration for CVE-2025-21826

GitHub Security Advisory for CVE-2025-21826

GHSA-8376-779w-5hcf · Severity: medium — In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: reject...

OS Trackers for CVE-2025-21826

vendor priority summary link
debian not yet assigned CVE-2025-21826 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6. https://security-tracker.debian.org/tracker/CVE-2025-21826
redhat medium https://access.redhat.com/security/cve/CVE-2025-21826
suse medium CVE-2025-21826 severity moderate: SUSE including 52 source package names (cluster-md-kmp-default, dlm-kmp-default, …), 293 product×package rows across 54 product lines (SLES-LTSS-TERADATA 15 SP2, SUSE Linux Enterprise High Availability Extension 12 SP5, … (54 product lines)): Known Not Affected 267, Fixed 26. https://www.suse.com/security/cve/CVE-2025-21826/
ubuntu medium CVE-2025-21826 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1551 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 1145, released 168, ignored 148, not-affected 89, needed 1. https://ubuntu.com/security/CVE-2025-21826

Affected software / configurations for CVE-2025-21826

Vendor Product Version Raw CPE
linux linux_kernel >= 5.10.209, < 5.10.235 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 5.15.148, < 5.15.179 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.1.75, < 6.1.129 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.6.14, < 6.6.76 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.7.2, < 6.12.13 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.13, < 6.13.2 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

References for CVE-2025-21826

URL Tags
https://git.kernel.org/stable/c/1b9335a8000fb70742f7db10af314104b6ace220 Patch
https://git.kernel.org/stable/c/2ac254343d3cf228ae0738b2615fedf85d000752 Patch
https://git.kernel.org/stable/c/49b7182b97bafbd5645414aff054b4a65d05823d Patch
https://git.kernel.org/stable/c/5083a7ae45003456c253e981b30a43f71230b4a3 Patch
https://git.kernel.org/stable/c/6b467c8feac759f4c5c86d708beca2aa2b29584f Patch
https://git.kernel.org/stable/c/82e491e085719068179ff6a5466b7387cc4bbf32 Patch
https://git.kernel.org/stable/c/ab50d0eff4a939d20c37721fd9766347efcdb6f6 Patch
https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
https://cert-portal.siemens.com/productcert/html/ssa-265688.html
https://cert-portal.siemens.com/productcert/html/ssa-503939.html
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