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CVE-2026-68295
LoongArch: BPF: Zero-extend signed ALU32 div/mod results
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem arch/loongarch. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-68295 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 | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
ALU32 operations write a 32-bit result and leave the upper 32 bits of the BPF register zero. The LoongArch JIT sign-extends the result of signed ALU32 BPF_DIV and BPF_MOD (off=1), so a negative 32-bit quotient or remainder leaves bits 63:32 set in JITted code while the verifier and interpreter model those bits as zero. Keep sign-extension on the operands, which signed divide needs, and zero-extend the ALU32 result after the divide or modulo instruction, matching the unsigned ALU32 div/mod paths and every other ALU32 operation in this JIT.
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.
arch/loongarch/net/bpf_jit.c
- What this is
- BPF JIT for LOONGARCHMAINTAINERS section matched on arch/loongarch/net/ · bpf@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_BPF_JIT /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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormy
- trixie, forky, sidYnot built on s390x/s390x
- y
- built into the kernel image on every flavour - only a patch removes it
- Y
- built in where it is built at all; some flavours do not build it
- Build switch
- CONFIG_BPF_JIT
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
- 2026-08-10 (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 6.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- arch/loongarch
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.7 | 6.18.57 | 16656c3d7346 |
| 6.7 | 7.1.6 | 716cb29dbed4 |
| 6.7 | 7.2 | dacd348b8a99 |
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 in the LoongArch eBPF JIT and is reached by loading a BPF program via the bpf(BPF_PROG_LOAD) syscall, which requires local access to the system. No network-facing path emits JITted signed ALU32 div/mod on behalf of a remote peer.
- AC:LAttack complexity, low
- The attacker fully controls the BPF instruction sequence and the divisor/dividend, so producing a negative signed ALU32 quotient or remainder is deterministic and repeatable with no race, timing, or memory-layout dependency.
- PR:LPrivileges required, low
- Loading an eBPF program requires only an unprivileged local user where unprivileged BPF is permitted, or CAP_BPF/CAP_SYS_ADMIN which is reachable via user namespaces on many deployments; no real root in the init namespace is needed.
- UI:NUser interaction, none
- The attacker loads and runs its own BPF program; no action by any other user or administrator is required at any point.
- S:UScope, unchanged
- The verifier bypass and resulting memory corruption stay within the kernel's own security authority on the same host, giving kernel-level privilege escalation rather than crossing a VM, IOMMU, or hypervisor boundary.
- C:HConfidentiality impact, high
- The verifier models bits 63:32 of the ALU32 result as zero while the JIT leaves them set, so a later ALU64 shift lets the verifier conclude a register is constant zero when it is really 0xFFFFFFFF; using it as a pointer offset yields an attacker-controlled out-of-bounds read of arbitrary kernel memory.
- I:HIntegrity impact, high
- The same verifier/JIT range mismatch produces an out-of-bounds pointer that passes verification for stores as well as loads, giving an arbitrary kernel write primitive usable for control-flow hijacking and full privilege escalation.
- A:HAvailability impact, high
- Out-of-bounds accesses through the mis-tracked register readily fault on unmapped or protected kernel addresses, causing an oops or panic, and the corruption can be repeated at will to bring the system down.