CVE-2025-21960Network attack vector

Kernel warning via duplicate checksum-state update

Published Apr 1, 2025 · Updated Aug 5, 2026

Improper state handling in Linux 5.19 and later allows remote attackers to trigger a kernel warning with crafted network traffic. On the bnxt XDP multi-buffer PASS path, bnxt_xdp_build_skb sets ip_summed to CHECKSUM_UNNECESSARY before bnxt_rx_pkt expects CHECKSUM_NONE and updates it again. Reachability requires a supported bnxt adapter, checksum offload, and an attached XDP multi-buffer program returning XDP_PASS; the published reproducer reports a warning rather than corruption or data exposure.

CVSS severity7.5
High
EPSS probability0.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper state handling in Linux 5.19 and later allows remote attackers to trigger a kernel warning with crafted network traffic. On the bnxt XDP multi-buffer PASS path, bnxt_xdp_build_skb sets ip_summed to CHECKSUM_UNNECESSARY before bnxt_rx_pkt expects CHECKSUM_NONE and updates it again. Reachability requires a supported bnxt adapter, checksum offload, and an attached XDP multi-buffer program returning XDP_PASS; the published reproducer reports a warning rather than corruption or data exposure.

The record

CVE
CVE-2025-21960
Published
Apr 1, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 1, 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=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <44578bc6460b8fca530fc7bd5897c115d9bd27e2
  2. Affected versionversion=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <5b57ed14a1b85e7ab0074d9668a0baa6c94826c7
  3. Affected versionversion=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <c03e7d05aa0e2f7e9a9ce5ad8a12471a53f941dc
  4. Affected versionversion=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <e8e3e03d69f2420eaa578199a65d281c58867105
  5. Affected versionversion=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <ee086c8e775f9690282e3d26471dbcfd5dad5a6a
  6. Affected versionversion=5.19

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <44578bc6460b8fca530fc7bd5897c115d9bd27e2; version=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <5b57ed14a1b85e7ab0074d9668a0baa6c94826c7; version=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <c03e7d05aa0e2f7e9a9ce5ad8a12471a53f941dc; version=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <e8e3e03d69f2420eaa578199a65d281c58867105; version=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <ee086c8e775f9690282e3d26471dbcfd5dad5a6a; version=5.19

Published CVSS scores

7.5kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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.

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No observations available

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

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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