CVE-2026-93048

What the bug is

mtd_add_partition() does not reject the special offset value MTDPART_OFS_RETAIN (-3), which leads to a WARN_ON in add_mtd_device() when called through the BLKPG ioctl on NAND devices. The RETAIN value depends on cur_offset being the end of the previous partition, but in the dynamic partition path cur_offset equals the offset argument itself, causing undefined behavior. Commit 5daa7b21496a ("mtd: prepare partition add and del functions for ioctl requests") introduced mtd_add_partition() and correctly rejected MTDPART_OFS_APPEND (-1) and MTDPART_OFS_NXTBLK (-2), since those special offsets rely on cur_offset tracking the previous partition's end. However, commit 1a31368bf92e ("mtd: add a flags for partitions which should just leave smth. after them") later added MTDPART_OFS_RETAIN (-3) for the static partition table path without updating mtd_add_partition() to also reject this value. With offset=-3 passed via BLKPG, the RETAIN size calculation in allocate_partition() underflows (parent_size - 0xFFFFFFFFFFFFFFFD = parent_size + 3). If the underflow result does not appear to leave enough space, allocate_partition() jumps to out_register via goto, skipping erasesize initialization. This results in erasesize=0, which triggers: WARN_ON((!mtd->erasesize || !master->_erase) && !(mtd->flags & MTD_NO_ERASE)) in add_mtd_device(). If the underflow result appears to leave enough space, a bogus partition size is calculated, but the "out of reach" sanity check catches the invalid offset and creates a disabled empty partition (offset=0, size=0) instead of returning an error. Fix this by adding MTDPART_OFS_RETAIN to the rejection list in mtd_add_partition(), consistent with the existing handling of APPEND and NXTBLK.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/mtd/mtdpart.c

What this is

MEMORY TECHNOLOGY DEVICES (MTD)MAINTAINERS section matched on drivers/mtd/ · linux-mtd@lists.infradead.org · Maintained

Kernel module

mtd

Check it on the machine

grep -w CONFIG_MTD /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

lsmod | grep -w mtd

Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.

Show whether Debian builds this, per release

Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.

• bookworm, trixie, forky, sid, bookworm · linux-6.12Bnot built on amd64/cloud-amd64, arm64/cloud-arm64

B

built in on some, a module on others, absent on the rest

Build switch

CONFIG_MTD

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-09-17 (31 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.21%, higher than 10.6% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/mtd

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
3.2	5.10.270	701c3ae7273e
3.2	5.15.221	6aaab2ace3f7
3.2	6.1.188	181c1bff940e
3.2	6.6.157	a536eb57be58
3.2	6.12.110	e204e5c49a01
3.2	6.18.52	398aca2f9012
3.2	7.2.6	c645f6dd1af2
3.2	7.3	b759d5bb6265

Debian advisories