Bug 2507079 (CVE-2026-64267) - CVE-2026-64267 kernel: fuse: avoid 32-bit prune notification count wrap
Summary: CVE-2026-64267 kernel: fuse: avoid 32-bit prune notification count wrap
Keywords:
Status: NEW
Alias: CVE-2026-64267
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-07-25 10:03 UTC by OSIDB Bzimport
Modified: 2026-07-30 05:03 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


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Description OSIDB Bzimport 2026-07-25 10:03:53 UTC
In the Linux kernel, the following vulnerability has been resolved:

fuse: avoid 32-bit prune notification count wrap

FUSE_NOTIFY_PRUNE validates the nodeid payload length with:

    size - sizeof(outarg) != outarg.count * sizeof(u64)

On 32-bit kernels, size_t is also 32 bits, so the daemon-controlled
count multiplication can wrap.  A prune notification with count
0x20000000 and no nodeid payload passes the check, enters the copy
loop, and asks the device copy path to read nodeids that are not
present in the userspace write buffer.  In QEMU this reaches the
fuse_copy_fill() BUG_ON(!err) path.

Validate the payload length with array_size() instead.  That accepts
exactly the same valid messages, but avoids wrapping arithmetic before
the copy loop consumes the count.


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