CVE-2025-21789

Kernel data disclosure or crash via negative length

Published Feb 27, 2025 · Updated Aug 5, 2026

Out-of-bounds read in Linux 6.4 and later affected LoongArch branches allows local users to disclose kernel data or crash the system. The LoongArch do_csum function tests only len == 0, so a negative length reaches checksum arithmetic, causes an undefined shift, and reads beyond the supplied buffer. Exploitation requires local AF_PACKET or TUN socket access with virtio_net_hdr; leaked heap bytes can enter an outgoing checksum, while hardened kernels can panic.

CVSS severity7.3
High
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Out-of-bounds read in Linux 6.4 and later affected LoongArch branches allows local users to disclose kernel data or crash the system. The LoongArch do_csum function tests only len == 0, so a negative length reaches checksum arithmetic, causes an undefined shift, and reads beyond the supplied buffer. Exploitation requires local AF_PACKET or TUN socket access with virtio_net_hdr; leaked heap bytes can enter an outgoing checksum, while hardened kernels can panic.

The record

CVE
CVE-2025-21789
Published
Feb 27, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 27, 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=6.4
  2. Affected versionversion=69e3a6aa6be21de6aaf38130fad97ecde34a193c <6287f1a8c16138c2ec750953e35039634018c84a
  3. Affected versionversion=69e3a6aa6be21de6aaf38130fad97ecde34a193c <964a8895704a22efc06a2a3276b624a5ae985a06
  4. Affected versionversion=69e3a6aa6be21de6aaf38130fad97ecde34a193c <9f15a8df542c0f08732a67d1a14ee7c22948fb97
  5. Affected versionversion=69e3a6aa6be21de6aaf38130fad97ecde34a193c <d6508ffff32b44b6d0de06704034e4eef1c307a7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.4; version=69e3a6aa6be21de6aaf38130fad97ecde34a193c <6287f1a8c16138c2ec750953e35039634018c84a; version=69e3a6aa6be21de6aaf38130fad97ecde34a193c <964a8895704a22efc06a2a3276b624a5ae985a06; version=69e3a6aa6be21de6aaf38130fad97ecde34a193c <9f15a8df542c0f08732a67d1a14ee7c22948fb97; version=69e3a6aa6be21de6aaf38130fad97ecde34a193c <d6508ffff32b44b6d0de06704034e4eef1c307a7

Published CVSS scores

7.3LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo