CVE-2025-21873

System crash via erroneous ARPMB reply length

Published Mar 27, 2025 · Updated May 11, 2026

Denial of service in the Linux kernel UFS BSG path allows local users to crash the system by submitting a failing ARPMB command. The ufs_bsg_request function sets job->reply_len when ufs_bsg_exec_advanced_rpmb_req returns an error, causing bsg_transport_sg_io_fn to copy an invalid reply and trigger a hardened usercopy abort. Reaching the flaw requires local access to issue an advanced RPMB request against a UFS device without ARPMB support; the consequence is a kernel crash and service interruption.

CVSS severity5.5
Medium
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

Denial of service in the Linux kernel UFS BSG path allows local users to crash the system by submitting a failing ARPMB command. The ufs_bsg_request function sets job->reply_len when ufs_bsg_exec_advanced_rpmb_req returns an error, causing bsg_transport_sg_io_fn to copy an invalid reply and trigger a hardened usercopy abort. Reaching the flaw requires local access to issue an advanced RPMB request against a UFS device without ARPMB support; the consequence is a kernel crash and service interruption.

The record

CVE
CVE-2025-21873
Published
Mar 27, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 27, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=6.3
  2. Affected versionversion=6ff265fc5ef660499e0edc4641647e99eed3f519 <32fb5ec825f6f76bc28902181c65429a904a07fe
  3. Affected versionversion=6ff265fc5ef660499e0edc4641647e99eed3f519 <59455f968c1004ed897ba873237657745d81ce0f
  4. Affected versionversion=6ff265fc5ef660499e0edc4641647e99eed3f519 <7e3c96ff5c5f3206984ed077b2aa8c9b7c4e0327
  5. Affected versionversion=6ff265fc5ef660499e0edc4641647e99eed3f519 <f27a95845b01e86d67c8b014b4f41bd3327daa63

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.3; version=6ff265fc5ef660499e0edc4641647e99eed3f519 <32fb5ec825f6f76bc28902181c65429a904a07fe; version=6ff265fc5ef660499e0edc4641647e99eed3f519 <59455f968c1004ed897ba873237657745d81ce0f; version=6ff265fc5ef660499e0edc4641647e99eed3f519 <7e3c96ff5c5f3206984ed077b2aa8c9b7c4e0327; version=6ff265fc5ef660499e0edc4641647e99eed3f519 <f27a95845b01e86d67c8b014b4f41bd3327daa63

Published CVSS scores

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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