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CVE-2026-53081
bpf: Enforce regsafe base id consistency for BPF_ADD_CONST scalars
Published 2026-06-24 (4 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-2026-53081 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 | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When regsafe() compares two scalar registers that both carry BPF_ADD_CONST, check_scalar_ids() maps their full compound id (aka base | BPF_ADD_CONST flag) as one idmap entry. However, it never verifies that the underlying base ids, that is, with the flag stripped are consistent with existing idmap mappings. This allows construction of two verifier states where the old state has R3 = R2 + 10 (both sharing base id A) while the current state has R3 = R4 + 10 (base id C, unrelated to R2). The idmap creates two independent entries: A->B (for R2) and A|flag->C|flag (for R3), without catching that A->C conflicts with A->B. State pruning then incorrectly succeeds. Fix this by additionally verifying base ID mapping consistency whenever BPF_ADD_CONST is set: after mapping the compound ids, also invoke check_ids() on the base IDs (flag bits stripped). This ensures that if A was already mapped to B from comparing the source register, any ADD_CONST derivative must also derive from B, not an unrelated C.
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/verifier.c
- What this is
- BPF [CORE]MAINTAINERS section matched on kernel/bpf/verifier.c · bpf@vger.kernel.org · Maintained
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
- 2026-06-24 (4 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
- 0.18%, 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 |
|---|---|---|
| 6.11 | 6.12.91 | 13c02881e49a |
| 6.11 | 6.18.33 | 691adf738817 |
| 6.11 | 7.0.10 | 7d73c72cccac |
| 6.11 | 7.1 | 2f2ec8e7730e |
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 vulnerable verifier path is reached by a local attacker through the bpf() syscall with BPF_PROG_LOAD, not by remote packets or adjacent/physical input. The crafted program then drives verifier state pruning into regsafe()/check_scalar_ids().
- AC:LAttack complexity, low
- Exploitation depends on constructing specific BPF instructions and verifier states, but there is no race or external condition outside the attacker's control. The verifier behavior is deterministic once the crafted program is submitted.
- PR:LPrivileges required, low
- The affected BPF_ADD_CONST tracking is gated on privileged BPF loading through CAP_BPF or an equivalent BPF token, but BPF tokens can delegate this capability into user namespaces in realistic containerized deployments. Under the required highest-severity reasonable scenario, this is low privilege rather than init-namespace root only.
- UI:NUser interaction, none
- No victim action is required; the attacker submits and executes the crafted BPF program directly through local kernel interfaces. Loading and triggering the program are attacker-controlled.
- S:UScope, unchanged
- The vulnerability is a kernel BPF verifier flaw that affects the same kernel security authority. It does not cross a separate scope such as guest-to-host or IOMMU isolation.
- C:HConfidentiality impact, high
- An unsound verifier state-pruning decision can allow an unsafe BPF program to pass validation, enabling kernel memory reads through invalid bounds or scalar relationship assumptions. BPF verifier bypasses are generally exploitable for high-impact information disclosure.
- I:HIntegrity impact, high
- By accepting an unsafe BPF program, the verifier can permit memory accesses or control effects that should have been rejected, supporting arbitrary kernel memory modification or code execution. This is a high-integrity kernel compromise scenario.
- A:HAvailability impact, high
- Even if not fully weaponized for read/write primitives, an unsafe accepted BPF program can crash or panic the kernel through invalid memory access. Kernel crash availability impact is high.