CVE-2025-71306: Linux Kernel Buffer Overflow Vulnerability

CVE-2025-71306 Overview

CVE-2025-71306 is a stack out-of-bounds read vulnerability in the Linux kernel's Integrity Measurement Architecture (IMA) subsystem. The flaw resides in the is_bprm_creds_for_exec() helper invoked by ima_appraise_measurement(). Kernel Address Sanitizer (KASAN) detected the issue when a container_of() macro was applied to a *file pointer that did not belong to a linux_binprm structure. This offset calculation reads past the bounds of the file object on the kernel stack. The vulnerability has been resolved upstream by passing an explicit bprm_is_check boolean rather than deriving context through pointer arithmetic.

Critical Impact
A local process triggering IMA appraisal paths can cause the kernel to perform an out-of-bounds stack read, potentially leading to information disclosure or kernel instability.

Affected Products

Linux kernel versions containing the affected IMA appraisal logic prior to the fix
Distributions shipping kernels with IMA appraisal enabled
Systems using IMA policy that exercises the is_bprm_creds_for_exec() code path

Discovery Timeline

2026-05-27 - CVE-2025-71306 published to NVD
2026-05-27 - Last updated in NVD database

Technical Details for CVE-2025-71306

Vulnerability Analysis

The Linux kernel's IMA subsystem appraises files during execution and other security-sensitive operations. Inside ima_appraise_measurement(), the helper is_bprm_creds_for_exec() attempted to recover a linux_binprm structure by applying container_of() to a *file pointer. When the caller did not pass a file field that was embedded in a linux_binprm, the macro computed an invalid base address. KASAN flagged the resulting read as a stack out-of-bounds access at offset 24 within the ima_appraise_measurement stack frame, reading one byte beyond the file object [CWE-125].

The stack frame disclosed by KASAN contained two objects: file at offsets [48, 56) and hash at offsets [80, 148). The faulty pointer arithmetic produced an address that aliased neither object cleanly, triggering the sanitizer report under a sudo execution path (task sudo/550).

Root Cause

The defect stems from using container_of() on a pointer whose container type cannot be guaranteed by the caller. is_bprm_creds_for_exec() assumed every file * argument originated from a linux_binprm.file field. When process_measurement() was invoked outside the BPRM_CHECK hook, that assumption failed, and the macro's negative offset subtraction produced a stack address outside any valid object.

Attack Vector

The vulnerability is reachable through standard file appraisal flows on systems with IMA appraisal policy enabled. A local user invoking operations that route through process_measurement() without a backing linux_binprm can trigger the unsafe pointer reconstruction. The patch replaces the implicit type recovery with an explicit bprm_is_check boolean propagated from the caller. When process_measurement() is invoked with a valid linux_binprm pointer and BPRM_CHECK, the flag is set to true; otherwise it defaults to false, eliminating the unsafe container_of() invocation.

No public exploit code or proof-of-concept has been published for CVE-2025-71306. See the Kernel Git Commit Details and Kernel Git Commit Changes for the upstream resolution.

Detection Methods for CVE-2025-71306

Indicators of Compromise

KASAN reports referencing stack-out-of-bounds in ima_appraise_measurement in kernel logs (dmesg, /var/log/kern.log).
Unexpected kernel oops or panic traces involving ima_appraise_measurement+0x12dc/0x16a0 and is_bprm_creds_for_exec.
IMA audit records with anomalous appraisal failures correlated to non-exec file accesses.

Detection Strategies

Enable KASAN on test or staging kernels to surface the out-of-bounds read during regression testing.
Collect and centralize kernel ring buffer output and audit integrity subsystem messages for IMA-related traces.
Correlate sudo and other privileged process executions with IMA appraisal events to identify abnormal patterns.

Monitoring Recommendations

Forward /var/log/audit/audit.log and kernel logs to a centralized log analytics or SIEM platform for retention and alerting.
Alert on kernel crash signatures referencing ima_appraise_measurement or KASAN stack-out-of-bounds reports.
Track kernel package versions across the fleet to identify hosts still running pre-patch builds.

How to Mitigate CVE-2025-71306

Immediate Actions Required

Inventory Linux hosts and identify kernels that predate the IMA appraisal fix referenced in the upstream commits.
Schedule and deploy distribution kernel updates that backport the bprm_is_check boolean change to process_measurement().
Reboot affected systems after patch installation so the corrected kernel image takes effect.

Patch Information

The fix is committed upstream in the Linux kernel stable tree. Refer to the Kernel Git Commit Details and Kernel Git Commit Changes for the patch content. Apply vendor-provided kernel updates from your Linux distribution maintainer once available.

Workarounds

Where patching is not immediately possible, review IMA policy and disable appraisal rules that exercise the affected code path on non-critical systems.
Restrict local access on systems with IMA appraisal enabled to limit who can trigger the vulnerable path.
Enable kernel hardening features such as CONFIG_FORTIFY_SOURCE and stack protectors to reduce the impact of out-of-bounds reads.

bash

# Verify currently running kernel version and IMA configuration
uname -r
cat /sys/kernel/security/ima/policy 2>/dev/null | head -n 20
dmesg | grep -i "ima_appraise_measurement\|KASAN"