CVE-2026-98124 smb/client: invalidate fscache for fallocate range operations

What is CVE-2026-98124?

CVE-2026-98124 is a medium-severity vulnerability in Linux kernel, published on 25 Sep 2026. 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:

smb/client: invalidate fscache for fallocate range operations

smb3_zero_range(), smb3_punch_hole(), smb3_insert_range(), and smb3_collapse_range() modify file contents through server-side range operations. These operations discard the affected page cache, but leave the FS-Cache cookie valid, so a later read may return data cached before the range operation.

Fix this by invalidating FS-Cache after outstanding I/O has completed and before modifying the file on the server.

Run the following as root on a CIFS mount with fsc enabled and an active CacheFiles backend:

bash -c ' MNT=/mnt/cifs FILE="$MNT/repro"

# Generate four 1 MiB random blocks: [A][B][C][D]. dd if=/dev/urandom of=/tmp/src bs=1M count=4 status=none

# Expected contents after zeroing B: [A][zero][C][D]. cp /tmp/src /tmp/expected dd if=/dev/zero of=/tmp/expected bs=1M seek=1 count=1 \ conv=notrunc status=none cp /tmp/src "$FILE"

# Populate FS-Cache, then discard the page cache. sync echo 1 > /proc/sys/vm/drop_caches cat "$FILE" > /dev/null sync echo 1 > /proc/sys/vm/drop_caches

fallocate --zero-range -o 1M -l 1M "$FILE"

if cmp -s /tmp/expected "$FILE"; then echo "readback: OK" else echo "readback: STALE DATA" fi '

Before this change, the readback differs from /tmp/expected:

readback: STALE DATA

After this change, it matches:

readback: OK

Weakness: CWE-672

Which versions are affected by CVE-2026-98124?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-98124?

Apply the vendor's patch.

Is CVE-2026-98124 being exploited?

There is no known exploitation of CVE-2026-98124 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-104756, BELL-CVE-2026-98124, DEBIAN-CVE-2026-98124, GHSA-wcf3-p4hx-gg65, UBUNTU-CVE-2026-98124.