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CVE-2026-74354
bpf: Take mmap_lock in zap_pages()
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem kernel/bpf. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-74354 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
zap_vma_range() requires the owning mm's mmap_lock to be held. Taking mmap_read_lock under arena->lock would AB-BA against arena_vm_close() and arena_map_mmap(), both of which run with mmap_write_lock held and then acquire arena->lock. Instead drop arena->lock, mmget_not_zero() the vma's mm, take mmap_read_lock, and re-resolve the vma via find_vma() since it may have been unmapped or replaced while waiting. Track processed vmls with a per-call generation in vml->zap_gen and serialize zap_pages() callers with a new arena->zap_mutex so concurrent callers on different uaddr ranges do not mark each other's vmls processed before the zap is done.
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/arena.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 with an answer below compiles the affected file into the kernels it ships. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookworm?
- trixie, forky, sidy
- ?
- not established - no Makefile entry for the affected file
- y
- built into the kernel image on every flavour - only a patch removes it
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- 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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.4% 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 |
|---|---|---|
| 6.9 | 7.1.5 | 36b1d997866f |
| 6.9 | 7.2 | 80b89d0226a0 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The flaw is reached only via local bpf(2) syscalls: creating a BPF_MAP_TYPE_ARENA, loading a JIT BPF program using bpf_arena_free_pages(), mmap()ing the arena, and executing that program, which calls zap_pages() and zap_vma_range() without mmap_lock.
- AC:LAttack complexity, low
- Exploitation requires racing page unmap with concurrent VMA teardown; the attacker controls both sides by running bpf_arena_free_pages() from BPF while another thread or process concurrently munmap()s or remaps the same arena mapping.
- PR:LPrivileges required, low
- Arena map creation requires CAP_BPF and verifier-enforced CAP_BPF plus CAP_PERFMON (bpf_allow_ptr_leaks), not init-namespace root; these capabilities are obtainable by an unprivileged user via user namespaces or perf-group membership on typical systems.
- UI:NUser interaction, none
- No victim interaction is required beyond the attacker loading their own BPF program and mmaping their own arena; triggering the race is fully automated once those attacker-controlled setup steps are done.
- S:UScope, unchanged
- Impact is confined to kernel memory management and process address spaces on the host; it does not cross a VM, container, or IOMMU security boundary into a separate authority such as a hypervisor host escape.
- C:HConfidentiality impact, high
- Calling zap_vma_range() without mmap_lock races with munmap and page faults, enabling stale VMA use, page-table corruption, and use-after-free conditions that can be leveraged for arbitrary kernel or cross-process memory disclosure.
- I:HIntegrity impact, high
- Unsynchronized PTE zapping and rmap updates can corrupt page tables and VMA metadata, providing memory corruption primitives that can be developed into arbitrary kernel writes and control-flow hijacking.
- A:HAvailability impact, high
- The mmap_lock violation can cause kernel oopses, panics, or hung memory management from inconsistent page tables and invalid VMA access during concurrent unmap operations.