CVE-2026-89459
CVE-2026-89459 is a security vulnerability. O3 Security confirms whether CVE-2026-89459 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
In the Linux kernel, the following vulnerability has been resolved: s390/percpu: Fix MVIY_PERCPU() with older binutils Commit a737737cdb9c ("s390/percpu: Infrastructure for more efficient this_cpu…
Description
In the Linux kernel, the following vulnerability has been resolved:
s390/percpu: Fix MVIY_PERCPU() with older binutils
Commit a737737cdb9c ("s390/percpu: Infrastructure for more efficient this_cpu operations") introduced MVIY_PERCPU(), which stringifies arguments that are already C string literals. This generates an assembler macro invocation with whitespace-separated quoted arguments:
GEN_MVIY "459712" "%r3"
GNU as versions prior to binutils 2.39 drop the separating whitespace between quoted macro arguments during input scrubbing. They consequently parse the invocation as a single argument and emit repeated warnings:
Warning: missing closing `"'
The .ifc in GEN_MVIY never matches and GNU as exits successfully without emitting the mviy instruction. As a result, the interrupted per-CPU sequence is not marked in lowcore and the exception return path cannot repair the per-CPU address register after migration.
All MVIY_PERCPU() callers pass C string literals. Use them directly and separate the assembler macro arguments with an explicit comma. The resulting invocation is:
GEN_MVIY 459712, %r3
This form is unambiguous for GNU as and LLVM's integrated assembler. This behavior was fixed in GNU as from binutils 2.39, but Linux supports binutils 2.30.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-89459 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-89459 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-89459. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-89459 in your dependencies?
O3 detects CVE-2026-89459 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.