Bug 2482646 (CVE-2026-46124) - CVE-2026-46124 kernel: isofs: validate block number from NFS file handle in isofs_export_iget
Summary: CVE-2026-46124 kernel: isofs: validate block number from NFS file handle in i...
Keywords:
Status: NEW
Alias: CVE-2026-46124
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
unspecified
unspecified
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-05-28 11:07 UTC by OSIDB Bzimport
Modified: 2026-05-28 18:01 UTC (History)
2 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2026-05-28 11:07:29 UTC
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.


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