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CVE-2026-74364
bpf: Reject exclusive maps as inner maps in map-in-map
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-2026-74364 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| 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
An exclusive map (created with excl_prog_hash) is bound to a single program by hash: check_map_prog_compatibility() refuses to load any program whose digest does not match map->excl_prog_sha. That check only runs for maps a program references directly, i.e. its used_maps. A map reached at runtime through a map-of-maps is never in used_maps, and bpf_map_meta_equal() does not consider excl_prog_sha, so an exclusive map can be inserted into a non-exclusive outer map and then looked up and mutated by an unrelated program, bypassing the exclusivity guarantee. For the signed loader this defeats the metadata map exclusivity check added in the signed loader: the cached map->sha[] is validated against the signed hash while another program on a hostile host rewrites the frozen map's contents through the outer map.
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/map_in_map.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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Nsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.18%, higher than 7.1% 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 |
|---|---|---|
| 6.18 | 6.18.40 | 3a0f73d27a8d |
| 6.18 | 7.1.5 | 7c58ace08f18 |
| 6.18 | 7.2 | 9a3c3c49c333 |
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 through bpf(2) syscalls (BPF_MAP_CREATE, BPF_MAP_UPDATE_ELEM, BPF_PROG_LOAD) and runtime BPF helpers on map-in-map structures, which per kernel guidance is a local attack vector.
- AC:LAttack complexity, low
- Exploitation is a reliable, attacker-controlled sequence (create outer map-of-maps, insert exclusive inner map FD, load program referencing only outer map, lookup/mutate inner map) with no races or layout dependencies.
- PR:LPrivileges required, low
- Triggering the vulnerable map-in-map paths requires local BPF privileges (typically CAP_BPF); per kernel guidance this is Low because CAP_BPF can be obtained by unprivileged users via user namespaces, not only init-namespace root.
- UI:NUser interaction, none
- No victim interaction is required; a local attacker with BPF access can create the outer map, insert the exclusive inner map, and mutate it through an unrelated loaded program without actions by other users.
- S:UScope, unchanged
- The impact is bypass of BPF exclusive-map and signed-loader integrity controls within the kernel BPF subsystem, not crossing a VM, container-to-host, or IOMMU security boundary.
- C:HConfidentiality impact, high
- An unrelated BPF program can bpf_map_lookup_elem() an exclusive inner map via map-in-map indirection and read its full contents, including signed metadata and hashes that must remain confidential to unauthorized programs.
- I:HIntegrity impact, high
- The same indirection allows bpf_map_update_elem() on an exclusive map bound to a different program digest, defeating exclusivity and enabling rewrite of signed-loader metadata (map->sha[]) and other protected map state.
- A:NAvailability impact, none
- This is an access-control bypass without memory corruption, use-after-free, or kernel panic; exploitation does not inherently cause crashes, hangs, or denial of kernel availability.