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CVE-2026-64082
riscv: Fix register corruption from uninitialized cregs on error
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem arch/riscv. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64082 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 | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
compat_riscv_gpr_set() calls cregs_to_regs() unconditionally, even when user_regset_copyin() fails. Since cregs is an uninitialized stack variable, a copyin failure causes uninitialized stack data to be written into the target task's pt_regs, corrupting its register state and potentially leaking kernel stack contents. compat_restore_sigcontext() has the same issue: it calls cregs_to_regs() even when __copy_from_user() fails, leading to the same corruption of the signal-returning task's register state on error. Only call cregs_to_regs() when the user copy succeeds.
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/riscv/kernel/compat_signal.c
arch/riscv/kernel/ptrace.c
- What this is
- RISC-V ARCHITECTUREMAINTAINERS section matched on arch/riscv/ · linux-riscv@lists.infradead.org · Supported
Check it on the machine
grep -w CONFIG_COMPAT /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.
- bookwormYnot built on armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, i386/686, i386/686-pae, i386/rt/686-pae, ppc64el/powerpc64le
- trixieYnot built on armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64
- forky, sidYnot built on armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- bookworm · linux-6.12Ynot built on armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k
- Y
- built in where it is built at all; some flavours do not build it
- Build switch
- CONFIG_COMPAT
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
- 2026-07-19 (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 2.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- arch/riscv
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.19 | 6.1.187 | f2d88b0d7aeb |
| 5.19 | 6.6.156 | 66dedb6028c3 |
| 5.19 | 6.12.108 | 2a7d1daf2674 |
| 5.19 | 6.18.49 | 0599aa23734c |
| 5.19 | 7.0.11 | 9e020156833f |
| 5.19 | 7.1 | 6ebcbb53fc9b |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | 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 bug is only reachable through local kernel interfaces—compat_rt_sigreturn and ptrace(PTRACE_SETREGSET)—with no network, adjacent-radio, or physical-device code path involved.
- AC:LAttack complexity, low
- An attacker can reliably force the user copy to fail by racing munmap/mprotect against sigreturn or ptrace SETREGSET after access_ok, controlling both sides of the TOCTOU window.
- PR:LPrivileges required, low
- The lowest-privilege path is compat_rt_sigreturn, callable by any unprivileged 32-bit compat process on a CONFIG_COMPAT RISC-V system without capabilities or root.
- UI:NUser interaction, none
- Exploitation requires no victim interaction; a local attacker corrupts their own task’s registers via rt_sigreturn or a tracee they already control as parent/tracer.
- S:UScope, unchanged
- Impact is confined to kernel register-state corruption and information disclosure within the same OS security boundary, not a VM escape or cross-authority sandbox breakout.
- C:HConfidentiality impact, high
- On copy failure, uninitialized kernel stack data (up to the full compat_user_regs_struct) is written into pt_regs, leaking kernel memory contents into user-observable registers.
- I:HIntegrity impact, high
- The corruption overwrites all general-purpose registers in pt_regs—including program counter, stack pointer, and return address—constituting memory corruption exploitable for control-flow hijacking.
- A:HAvailability impact, high
- Corrupted pt_regs reliably cause faults, SIGSEGV delivery, or erratic kernel/user execution, and the condition is repeatable for persistent denial of service.