CVE-2025-21736 nilfs2: fix possible int overflows in nilfs_fiemap()

What is CVE-2025-21736?

CVE-2025-21736 is a medium-severity 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:

nilfs2: fix possible int overflows in nilfs_fiemap()

Since nilfs_bmap_lookup_contig() in nilfs_fiemap() calculates its result by being prepared to go through potentially maxblocks == INT_MAX blocks, the value in n may experience an overflow caused by left shift of blkbits.

While it is extremely unlikely to occur, play it safe and cast right hand expression to wider type to mitigate the issue.

Found by Linux Verification Center (linuxtesting.org) with static analysis tool SVACE.

Weakness: CWE-190

Which versions are affected by CVE-2025-21736?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-21736?

Apply the vendor's patch.

Is CVE-2025-21736 being exploited?

There is no known exploitation of CVE-2025-21736 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-57832, BELL-CVE-2025-21736, DEBIAN-CVE-2025-21736, GHSA-jj6f-649q-27mh, ROOT-OS-UBUNTU-2404-CVE-2025-21736, UBUNTU-CVE-2025-21736.