CVE-2026-53351: Linux Kernel RISC-V Ptrace Vulnerability

CVE-2026-53351 Overview

CVE-2026-53351 is a Linux kernel vulnerability affecting the RISC-V ptrace subsystem. The issue occurs in the REGSET_CFI register set handling during core dump operations. The kernel emits a warning through elf_core_dump in fs/binfmt_elf.c because the note name is missing. Maintainers resolved the issue by using USER_REGSET_NOTE_TYPE for REGSET_CFI, ensuring the note is properly named when the kernel writes ELF core files. The vulnerability is scoped to the RISC-V architecture and manifests during process termination or debugging workflows that produce core dumps.

Critical Impact
The flaw triggers a kernel WARNING during core dump generation on RISC-V systems, indicating incorrect ELF note metadata for Control Flow Integrity register state.

Affected Products

Linux kernel on RISC-V architecture with REGSET_CFI support
Kernel builds prior to commits 08200bef0983 and e3573f739e3d
Systems generating ELF core dumps for RISC-V processes

Discovery Timeline

2026-07-01 - CVE-2026-53351 published to NVD
2026-07-01 - Last updated in NVD database

Technical Details for CVE-2026-53351

Vulnerability Analysis

The vulnerability resides in the RISC-V ptrace implementation, specifically in how the REGSET_CFI register set is exposed to userspace and to the ELF core dump machinery. The kernel core dump code in fs/binfmt_elf.c validates that each register set note carries a name. When REGSET_CFI was added to expose Control Flow Integrity state on RISC-V, the register set definition did not include a note name field. As a result, elf_core_dump triggered a WARNING at line 1771 with the diagnostic [!note_name] during core dump generation.

The kernel log captures the warning as follows:

[54983.546369][ C7] WARNING: [!note_name] fs/binfmt_elf.c:1771 at elf_core_dump+0x910/0xf68, CPU#7: abort01/31982

The fix updates the REGSET_CFI definition to use the USER_REGSET_NOTE_TYPE macro, which supplies the required note type and name.

Root Cause

The root cause is missing note-name metadata on the REGSET_CFI register set entry within the RISC-V ptrace regset table. The core dump path assumes every regset it emits into the ELF note segment has a valid name, and enforces this with a WARN_ON. The REGSET_CFI entry did not satisfy that contract, producing a warning each time a RISC-V process with CFI state was dumped.

Attack Vector

There is no evidence of remote or local exploitation for code execution. The condition is triggered by legitimate core dump generation, such as an aborting process or a debugger request. The impact is limited to kernel log noise and potential taint of the running kernel from the WARNING, which can complicate downstream reliability analysis on RISC-V systems. The attack vector, according to the NVD entry, is not classified.

Detection Methods for CVE-2026-53351

Indicators of Compromise

Kernel log entries containing WARNING: [!note_name] fs/binfmt_elf.c:1771
Stack traces referencing elf_core_dump+0x910/0xf68 on RISC-V hosts
Recurring warnings correlated with process abort events and core file generation

Detection Strategies

Query dmesg and persistent syslog stores for the !note_name string on RISC-V kernels.
Monitor kernel taint flags to identify hosts that have triggered WARN_ON in the ELF core dump path.
Correlate core dump file creation timestamps with the appearance of the warning in kernel logs.

Monitoring Recommendations

Ship kernel logs from RISC-V endpoints into a centralized log platform and alert on the specific warning signature.
Track kernel version and architecture inventory to identify hosts running unpatched RISC-V builds.
Review core dump collection policies to understand blast radius on affected systems.

How to Mitigate CVE-2026-53351

Immediate Actions Required

Update Linux kernels on RISC-V systems to a version containing commits 08200bef0983ffed039ab399df0cba8d900ce5fc and e3573f739e3dadab57ec80488d07e05c8f6e82d3.
Inventory RISC-V hosts and confirm patch level using uname -r and distribution advisories.
Rebuild and redeploy any custom kernel trees that carry the RISC-V REGSET_CFI code.

Patch Information

The upstream fix modifies the RISC-V ptrace regset table so REGSET_CFI uses USER_REGSET_NOTE_TYPE. See the Kernel Git Repository Commit 08200bef and Kernel Git Repository Commit e3573f73 for the exact code changes.

Workarounds

Disable core dump generation on affected RISC-V hosts by setting ulimit -c 0 where core dumps are not required.
Suppress warning-based kernel panics by ensuring panic_on_warn is disabled on production RISC-V systems until a patched kernel is deployed.
Restrict ptrace usage through kernel.yama.ptrace_scope to reduce debugger-initiated core dump generation.

bash

# Verify kernel version and RISC-V architecture
uname -m
uname -r

# Temporarily disable core dumps to avoid the warning path
ulimit -c 0

# Ensure panic_on_warn is not enabled while patching is pending
sysctl -w kernel.panic_on_warn=0