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CVE-2026-64354
bpf: Validate BTF repeated field counts before expansion
Published 2026-07-25 (3 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-2026-64354 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 | 6.12.96-1 | Update the kernel and reboot. Fixed in 6.12.96-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4724-1 · 2026-08-07 · text | 6.12.100-1~deb12u1 | Update the kernel and reboot. DLA-4724-1 shipped the fix on 2026-08-07, in 6.12.100-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
btf_parse_struct_metas() walks user-supplied BTF during BPF_BTF_LOAD, and btf_repeat_fields() expands repeatable fields from array elements into the fixed BTF_FIELDS_MAX scratch array used by btf_parse_fields(). The remaining-capacity check performs the expanded field count calculation in u32. A malformed BTF can wrap that calculation, causing the check to pass even when the expanded field count exceeds the scratch array capacity. The following memcpy() can then write past the end of the array. Use checked addition and multiplication before copying repeated fields and reject impossible counts.
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/btf.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, sid, bookworm · linux-6.12y
- 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
- 2026-07-25 (3 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
- 0.13%, higher than 2.2% 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 |
|---|---|---|
| 6.12 | 6.12.96 | c5ff816d5f13 |
| 6.12 | 6.18.39 | cd407de2ef5d |
| 6.12 | 7.1.4 | ff77d013b737 |
| 6.12 | 7.2 | b9452b594fd3 |
| 6.11.6 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4724-1 | 2026-08-07 | bookworm 6.12.100-1~deb12u1 | tracker |
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 attacker reaches the vulnerable parser through the local bpf(BPF_BTF_LOAD) syscall; no network or physical path exists.
- AC:LAttack complexity, low
- A compact, deterministic malformed BTF object triggers the arithmetic wrap and immediate out-of-bounds memcpy without a race or uncontrollable condition.
- PR:LPrivileges required, low
- BPF_BTF_LOAD normally requires init-namespace CAP_BPF, but a delegated BPF token permits CAP_BPF in its user namespace. Thus a namespace-root attacker in a reasonably delegated container environment can reach it with low privileges.
- UI:NUser interaction, none
- The attacker invokes BPF_BTF_LOAD directly and requires no action from another user.
- S:UScope, unchanged
- The corruption occurs within the host kernel's security authority; resulting privilege escalation or container escape is standard kernel compromise rather than a CVSS scope change.
- C:HConfidentiality impact, high
- The attacker-influenced kernel-stack overflow can corrupt control data and plausibly enable kernel code execution, which would expose arbitrary kernel memory.
- I:HIntegrity impact, high
- The vulnerable memcpy performs a large out-of-bounds kernel-stack write using attacker-influenced metadata records, making control-flow corruption and arbitrary kernel modification defensible.
- A:HAvailability impact, high
- The expansion repeatedly overwrites beyond the stack array until it reaches control data, a guard page, or adjacent kernel memory, allowing a deterministic kernel oops, panic, or severe corruption.