CVE-2025-71139: Linux Kernel Privilege Escalation Flaw

CVE-2025-71139 Overview

A vulnerability has been identified in the Linux kernel's kexec subsystem involving Integrity Measurement Architecture (IMA) operations when memory allocation occurs in the Contiguous Memory Allocator (CMA) area. The issue manifests as a warning in kimage_map_segment() during ima_kexec_post_load() operations, potentially affecting system stability during kexec operations.

Critical Impact
Systems utilizing kexec with CMA-based memory allocation may experience kernel warnings and potential instability when IMA verification is performed on kexec segments allocated in CMA areas.

Affected Products

Linux kernel versions with CMA-based kexec allocation (commit 07d24902977e and later)
Systems with CMA area reserved via the cma= kernel command line option
Linux systems utilizing kexec file load with IMA enabled

Discovery Timeline

2026-01-14 - CVE CVE-2025-71139 published to NVD
2026-01-14 - Last updated in NVD database

Technical Details for CVE-2025-71139

Vulnerability Analysis

This vulnerability exists in the Linux kernel's kexec subsystem, specifically in the interaction between IMA (Integrity Measurement Architecture) and CMA (Contiguous Memory Allocator) based memory allocation. The issue was introduced when commit 07d24902977e ("kexec: enable CMA based contiguous allocation") changed the allocation behavior to place the kexec target address directly in the CMA area to avoid memory copying during the jump operation.

The problem arises because the kimage_map_segment() function assumes that IND_SOURCE pages exist for kexec segments and attempts to map them into a contiguous virtual address using vmap(). However, when segments are allocated directly in the CMA area, there is no IND_SOURCE for the kexec segment, causing the function to encounter an unexpected condition and trigger a kernel warning.

Root Cause

The root cause is an architectural assumption mismatch in the kimage_map_segment() function. When CMA-based contiguous allocation was implemented for kexec, it enabled direct allocation in the CMA area without intermediate IND_SOURCE pages. The IMA verification code path through ima_kexec_post_load() still relies on the legacy vmap() approach that expects IND_SOURCE pages to exist, creating a conflict when these pages are absent in CMA-allocated segments.

Attack Vector

This vulnerability is triggered during normal kexec operations rather than through external attack vectors. The condition occurs when:

The system has a reserved CMA area (either by default or via cma= kernel parameter)
A kexec file load operation is performed
The kexec target address is allocated within the CMA area
IMA performs post-load verification via ima_kexec_post_load()

The vulnerability results in a kernel warning at kimage_map_segment+0x144/0x198 during the __do_sys_kexec_file_load system call. While this is primarily a reliability issue rather than a security exploitation vector, it can impact system operations during kexec-based system updates or reboots.

Detection Methods for CVE-2025-71139

Indicators of Compromise

Kernel warning messages containing kimage_map_segment+0x144/0x198
Warning traces referencing ima_kexec_post_load in the call stack
kexec file load operations failing or producing warnings when CMA is enabled
System log entries showing WARNING: CPU: X PID: Y at kernel/kexec_core.c:1001

Detection Strategies

Monitor system logs (/var/log/kern.log, dmesg) for kernel warnings related to kimage_map_segment and ima_kexec_post_load
Implement automated log parsing to detect kexec-related kernel warnings during system updates
Check kernel boot parameters for cma= allocations which may trigger this condition
Review system behavior during kexec operations on systems with IMA enabled

Monitoring Recommendations

Enable kernel log monitoring for warnings in the kexec subsystem
Track kexec file load system calls on systems with CMA configured
Monitor IMA verification failures or warnings during kexec operations
Implement alerting for unexpected kernel warnings during system maintenance windows

How to Mitigate CVE-2025-71139

Immediate Actions Required

Update to a patched Linux kernel version containing the fix
Review systems utilizing kexec with CMA for potential impact
Monitor kexec operations for warnings until patches are applied
Consider temporarily disabling CMA for kexec if stability issues occur

Patch Information

The vulnerability has been addressed in the Linux kernel with patches that modify the IMA segment handling to use page_address() directly when the segment is allocated in the CMA area, rather than assuming IND_SOURCE pages exist.

Security patches are available through the following kernel commits:

Workarounds

If patching is not immediately possible, avoid using kexec on systems with CMA enabled
Temporarily remove the cma= kernel parameter if it was manually configured
Consider using traditional kexec memory allocation methods until the patch is applied
Implement kexec operations during planned maintenance windows to monitor for warnings

bash

# Check if CMA is configured on your system
cat /proc/cmdline | grep -o 'cma=[^ ]*'

# View current CMA allocation status
cat /proc/meminfo | grep Cma

# Update kernel to patched version (example for Debian/Ubuntu)
sudo apt update && sudo apt upgrade linux-image-$(uname -r)