CVE-2025-21789 LoongArch: csum: Fix OoB access in IP checksum code for negative lengths

What is CVE-2025-21789?

CVE-2025-21789 is a high-severity memory corruption vulnerability in Linux kernel, published on 27 Feb 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

LoongArch: csum: Fix OoB access in IP checksum code for negative lengths

Commit 69e3a6aa6be2 ("LoongArch: Add checksum optimization for 64-bit system") would cause an undefined shift and an out-of-bounds read.

Commit 8bd795fedb84 ("arm64: csum: Fix OoB access in IP checksum code for negative lengths") fixes the same issue on ARM64.

Weakness: CWE-125

Which versions are affected by CVE-2025-21789?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-21789?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2025-21789 being exploited?

There is no known exploitation of CVE-2025-21789 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-57896, BELL-CVE-2025-21789, DEBIAN-CVE-2025-21789, GHSA-fm6p-4m7g-f8f3, UBUNTU-CVE-2025-21789.