CVE-2026-98813

What the bug is

bpf_ma_set_dtor() duplicates map->record so that the bpf_mem_alloc destructor can release the special fields of hash and rhash map elements once the allocator frees them for good. btf_record_dup() only acquires references on kernel and module BTF. Fields whose types live in the map BTF keep pointing into it: a kptr to a local type refers to map->btf, and a list_head or rb_root field carries a value_rec owned by the struct meta table of map->btf. That borrowed state can outlive the map. When RCU callbacks are still in flight, bpf_mem_alloc_destroy() copies the allocator and defers the final drain, together with the destructor context, to a workqueue. bpf_map_free() then frees map->record and drops the map's BTF reference as soon as map_free() returns. Once the program that loaded the BTF is gone as well, the BTF is freed while the worker still uses the duplicate. The worker dereferences it through btf_is_kernel() and btf_find_struct_meta() in bpf_obj_free_fields() when destroying elements that were freed under RCU, and through btf_is_kernel() in btf_record_free() when releasing the context itself: BUG: KASAN: slab-use-after-free in btf_is_kernel+0x19/0x30 Read of size 1 at addr ffff88811505dce8 by task kworker/u16:2/50 Workqueue: events_unbound free_mem_alloc_deferred Call Trace: btf_is_kernel+0x19/0x30 btf_record_free+0xc7/0xf0 htab_dtor_ctx_free+0x1a/0x30 free_mem_alloc_no_barrier+0x39/0x230 free_mem_alloc_deferred+0x2a/0x40 process_scheduled_works+0x5ce/0x9d0 worker_thread+0x42a/0x5e0 kthread+0x1f5/0x230 ret_from_fork+0x1dd/0x390 ret_from_fork_asm+0x1a/0x30 Allocated by task 358: __kmalloc_cache_noprof+0x287/0x510 btf_new_fd+0xf7/0x3d0 __sys_bpf+0x487/0x840 Freed by task 0: kfree+0x186/0x560 rcu_core+0x6f6/0xd40 Freeing a map that still holds more elements than the allocator's high watermark is enough to get there, because the bulk free during teardown queues the RCU callback that makes bpf_mem_alloc_destroy() defer. Non-preallocated hash maps and resizable hash maps both register the destructor and are affected alike. Keep one reference on the map BTF in the destructor context. Every non-kernel pointer in the duplicated record is either map->btf or memory owned by it, so a single reference covers kptrs, list heads, and rb roots, and mirrors what bpf_map_meta_alloc() does for the duplicated record of an inner map. Release it only after the duplicated record has been freed: the worker is preemptible and not in an RCU read-side critical section, so dropping the last reference first would let the BTF be freed while btf_record_free() still reads its fields.

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

2026-10-18 (today)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

not scored

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
7.0	7.2.10	b506f5699e14
7.0	7.3	ab39974240a0
6.12.112	0	0
6.18.55	0	0