CVE-2026-80560
Received Received - Intake

Privilege Escalation in Linux Kernel via SR Bit Manipulation

Publication date: 2026-08-26

Last updated on: 2026-08-26

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: openrisc: signal: do not restore privileged SR bits on sigreturn restore_sigcontext() copies the whole supervision register (SR) from the signal frame and only clears SPR_SR_SM before the value is reloaded into the hardware SR (through ESR and l.rfe) on the return to user space. All other SR bits are left under user control. An unprivileged task can thus return from a signal handler through a crafted sigframe that clears SPR_SR_DME. With the data MMU disabled the CPU performs no translation or protection on data accesses, so the task gains read and write access to arbitrary physical memory, a local privilege escalation. SPR_SR_IME, SPR_SR_SUMRA, SPR_SR_LEE, SPR_SR_EPH and the cache-enable bits are exposed the same way. The ptrace GPR regset already refuses any change to SR for exactly this reason. Restore only the arithmetic flag bits (F, CY, OV) from the signal frame and take every privileged control bit from the SR the kernel saved on signal entry. Verified with qemu-system-or1k -M or1k-sim: before this change an unprivileged PoC clears SPR_SR_DME in rt_sigreturn and writes a marker to physical address 0x03000000 (beyond the kernel's mem=32M); afterwards the same PoC receives SIGSEGV and physical memory is unchanged.

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Meta Information

Published
2026-08-26
Last Modified
2026-08-26
Generated
2026-08-26
AI Q&A
2026-08-26
EPSS Evaluated
N/A
NVD
CVE-2026-80560
EUVD
EUVD-2026-66475

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel allows an unprivileged task to escalate privileges by manipulating the signal return process. The issue occurs when the kernel restores the supervision register (SR) from a signal frame without properly clearing privileged bits. An attacker can craft a signal frame that disables memory protection (SPR_SR_DME), granting access to arbitrary physical memory.

Detection Guidance

This vulnerability affects the Linux kernel's signal handling for the OpenRISC architecture. Detection requires checking if your system uses a vulnerable kernel version. Inspect the kernel version with uname -a and compare it against patched versions. No specific commands are provided for network detection as this is a local privilege escalation issue.

Impact Analysis

This vulnerability enables local privilege escalation. An attacker with basic user access could gain full control over the system by reading or writing to restricted memory locations. This could lead to complete system compromise, data theft, or installation of malware.

Mitigation Strategies

Update the Linux kernel to a patched version that addresses this issue. If immediate patching is not possible, restrict access to systems running vulnerable kernels or disable OpenRISC support if unused. Monitor for unusual privilege escalation attempts or unauthorized memory access.

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