CVE-2025-21961Public exploitNetwork attack vector

Remote service interruption via incorrect packet truesize

Published Apr 1, 2025 · Updated Aug 5, 2026

Availability flaw in Linux allows remote attackers to interrupt service with crafted jumbo packets on affected bnxt interfaces. bnxt_xdp_build_skb reads the fragment count after napi_build_skb has wiped skb_shared_info, then passes an understated truesize to xdp_update_skb_shared_info. Exposure requires a Broadcom NetXtreme interface with jumbo MTU and multi-buffer XDP returning XDP_PASS; traffic can trigger a panic when panic_on_warn is set or drive memory exhaustion otherwise.

CVSS severity7.5
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Availability flaw in Linux allows remote attackers to interrupt service with crafted jumbo packets on affected bnxt interfaces. bnxt_xdp_build_skb reads the fragment count after napi_build_skb has wiped skb_shared_info, then passes an understated truesize to xdp_update_skb_shared_info. Exposure requires a Broadcom NetXtreme interface with jumbo MTU and multi-buffer XDP returning XDP_PASS; traffic can trigger a panic when panic_on_warn is set or drive memory exhaustion otherwise.

The record

CVE
CVE-2025-21961
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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <19107e71be330dbccb9f8f9f4cf0a9abeadad802
  2. Affected versionversion=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <9f7b2aa5034e24d3c49db73d5f760c0435fe31c2
  3. Affected versionversion=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <b4679807c6083ade4d47f03f80da891afcb6ef62
  4. Affected versionversion=5.19

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <19107e71be330dbccb9f8f9f4cf0a9abeadad802; version=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <9f7b2aa5034e24d3c49db73d5f760c0435fe31c2; version=1dc4c557bfedfcdf7fc0c46795857773b7ad66e7 <b4679807c6083ade4d47f03f80da891afcb6ef62; version=5.19

Published CVSS scores

7.5Linux CNACVSS: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.

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1499.004Endpoint Denial of Service: Application or System Exploitation

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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