EUVD-2026-66475
GHSA-gfrq-95rp-6g53
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local code execution with low privileges sufficient to craft a signal frame; full C/I/A impact from arbitrary physical memory access after MMU bypass.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
5DescriptionCVE.org
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.
AnalysisAI
Local privilege escalation in the Linux kernel's OpenRISC signal return path allows any unprivileged local user to disable the Data MMU and gain arbitrary physical memory read/write access. The flaw exists in restore_sigcontext() on the OpenRISC (or1k) architecture, which fails to filter privileged Supervision Register (SR) bits copied from a user-controlled signal frame on sigreturn. …
Unlock full vulnerability intelligence
- Risk assessment & exploitation conditions
- Attack chain visualization
- Remediation with exact patch versions
- Threat intelligence from 22 sources
- Personal watchlist & email alerts
Free forever · No credit card required
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a low-privileged local account with the ability to execute code on a Linux system running the OpenRISC (or1k) architecture - either on real or1k hardware or under qemu-system-or1k emulation. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 7.8 score (AV:L/AC:L/PR:L/UI:N/C:H/I:H/A:H) is well-calibrated: a low-privileged local user can exploit this with straightforward signal-frame manipulation and no assistance from other users or processes. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An unprivileged user with a local shell on an OpenRISC system registers a signal handler, then on receipt of a signal constructs a malicious sigframe on the stack with the SPR_SR_DME bit cleared in the saved SR field before calling rt_sigreturn. After the kernel restores the crafted SR to hardware via l.rfe, the CPU performs no virtual-to-physical translation on data accesses, allowing the process to directly read and write physical memory - including the kernel's own data structures at arbitrary addresses - achieving full privilege escalation. … |
| Remediation | Update the Linux kernel to a patched stable release for your branch: 5.10.266, 5.15.217, 6.1.184, 6.6.153, 6.12.105, 6.18.46, 7.1.10, or 7.2. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all systems running Linux on OpenRISC processors and assess your exposure scope. …
Sign in for detailed remediation steps and compensating controls.
Threat intelligence, references, and detailed analysis are available after sign-in.
Same technique Privilege Escalation
View allShare
External POC / Exploit Code
Leaving vuln.today