CVE-2026-98036

What the bug is

rhtab_map_update_elem() initializes special fields after obtaining an element from bpf_mem_cache_alloc(). The allocator can return a fresh, zeroed unit, or recycle one from its RCU-pending lists before the registered destructor has run. A BPF program can retain a map-value pointer after deleting its element and initialize and arm a timer through that pointer. If the deleted unit is recycled, check_and_init_map_value() clears the only pointer to the timer. Neither a later deletion nor rhtab_mem_dtor() can then cancel it, and the callback can run with its key and value pointing into freed memory. Do not reinitialize special fields on insertion. Fresh allocator units are already zeroed. For recycled units, the special fields are ownership state that must remain visible to the eventual destructor. copy_map_value() already skips those fields, matching the non-preallocated hash-map path and the lifecycle established by commit 275c30bcee66 ("bpf: Don't reinit map value in prealloc_lru_pop"). [ kkd: Split out the fix and rewrote the commit log ]

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.

kernel/bpf/hashtab.c

What this is

BPF [GENERAL] (Safe Dynamic Programs and Tools)MAINTAINERS section matched on kernel/bpf/ · bpf@vger.kernel.org · Supported

Check it on the machine

grep -wE 'CONFIG_BPF|CONFIG_BPF_SYSCALL' /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.

Show whether Debian builds this, per release

Debian builds this code. Every release below compiles the affected file into the kernels it ships.

• bookworm, trixie, forky, sidy

y

built into the kernel image on every flavour - only a patch removes it

Build switches

CONFIG_BPF, CONFIG_BPF_SYSCALL

Reads as

all on means the file is compiled; any one off means it is not.

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

2026-09-25 (24 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.15%, higher than 4.3% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

unimportantsource

Subsystem

kernel/bpf

Upstream fixes

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

Introduced	Fixed in	Commit
7.2	7.2.7	6a5266b82882
7.2	7.3	5df46ddcb7b3