CVE-2025-5702

What it actually does

The optimized strcmp in glibc 2.39+ for Power10 writes to non-volatile vector registers v20-v31 without preserving caller state per the powerpc64le ABI, corrupting register contents and enabling control-flow changes or leakage of compared string data.

Why it matters to the business

Applications on affected Ubuntu systems may experience crashes, altered execution, or unintended data exposure until the kernel package is updated, though exploitation likelihood remains low.

How an attack unfolds

An attacker supplies crafted string inputs to a vulnerable strcmp call on a Power10 system; the unsaved register writes corrupt caller context, which can be leveraged to redirect execution or expose sensitive strings to other program regions.

How to fix it

Upgrade linux-hwe-5.4 on Ubuntu 18.04 LTS to version 5.4.0-125.141~18.04.1 or later; reboot after installation to activate the corrected kernel.

How to confirm the fix worked

Confirm the installed package version matches or exceeds 5.4.0-125.141~18.04.1 using package management tools and verify that glibc-linked binaries no longer exhibit register corruption symptoms under test workloads.

Typical attack path

1. Locate a process invoking strcmp on a Power10-based Ubuntu system with the vulnerable package
2. Trigger the function with inputs that exercise the Power10-optimized path
3. Observe or manipulate resulting register corruption to alter control flow or access leaked data

How to detect it

Review system and application logs for segmentation faults or abnormal behavior during string operations on Power10 systems; correlate with process crashes involving libc functions.

What your security team should do

• Apply the listed kernel update across all affected systems without delay
• Prioritize Power10 hardware for immediate patching
• Re-test critical applications that perform frequent string comparisons after deployment