What’s Vulnerable › Vulnerabilities

CVE-2026-46124: isofs: validate block number from NFS file handle in isofs_export_iget

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-28 · updated 2026-10-19
• Weakness: CWE-125

Description

In the Linux kernel, the following vulnerability has been resolved: isofs: validate block number from NFS file handle in isofs_export_iget isofs_fh_to_dentry() and isofs_fh_to_parent() pass an attacker- controlled block number (ifid->block or ifid->parent_block) from the NFS file handle to isofs_export_iget(), which only rejects block == 0 before calling isofs_iget() and ultimately sb_bread(). A crafted file handle with fh_len sufficient to pass the check added by commit 0405d4b63d08 ("isofs: Prevent the use of too small fid") can still drive the server to read any in-range block on the backing device as if it were an iso_directory_record. That earlier fix was assigned CVE-2025-37780. sb_bread() on an out-of-range block returns NULL cleanly via the EIO path, so there is no memory-safety violation. For in-range reads of adjacent-partition data on the same block device, the unrelated bytes end up in iso_inode_info fields that reach the NFS client as dentry metadata. The deployment surface (isofs exported over NFS from loop-mounted images) is narrow and requires an authenticated NFS peer, but the malformed-file-handle class is reportable as hardening next to the existing CVE-2025-37780 fix. Reject block >= ISOFS_SB(sb)->s_nzones in isofs_export_iget() so the check covers both isofs_fh_to_dentry() and isofs_fh_to_parent() call sites with a single line.

Affected products

• Linux kernel: from 5.4.293 before 5.5; from 5.10.237 before 5.10.258; from 5.15.181 before 5.15.209; from 6.1.135 before 6.1.175; from 6.6.88 before 6.6.140; from 6.12.25 before 6.12.88 — fixed in 5.10.258, 5.15.209, 5.5, 6.1.175, 6.12.88, 6.15

How to fix

Upgrade to a fixed version: Linux kernel 5.10.258, 5.15.209, 5.5, 6.1.175. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/0a1af74ae2177bda3aee0837a0546309aa539d0d
• https://git.kernel.org/stable/c/24376458138387fb251e782e624c7776e9826796
• https://git.kernel.org/stable/c/31dbb4ba0f719ae7774e4c0c95172c9bf81692f5
• https://git.kernel.org/stable/c/4c721a1d9b3c4fcaf59cc9b2281e3ec5a043e1a6
• https://git.kernel.org/stable/c/908a76f0b1038035e6ebb4f2293ce079f92e0a02
• https://git.kernel.org/stable/c/afbafeddf23db13fe2edb2d5c0bf4bbb13d7881b
• https://git.kernel.org/stable/c/bb0988ed4f2e26d59bbb58f644cb3a55b7521e21
• https://git.kernel.org/stable/c/ee0024f5a7e3c73aa253869fae9650ae054093ca
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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