EUVD-2026-76365
GHSA-mqmh-f84h-6j7h
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local-only trigger on s390 hardware compiled with old binutils (AC:H/AV:L); low-privilege process required; register corruption enables full C/I/A impact.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
Lifecycle Timeline
6DescriptionCVE.org
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.
AnalysisAI
Register corruption in Linux kernel s390/percpu silently drops the mviy instruction on kernels compiled with GNU binutils prior to 2.39, leaving the per-CPU address register unrepaired after CPU migration following an interrupt. Affected kernels are limited to IBM s390/zSeries architecture builds in the 7.2 lineage using the older toolchain. …
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Vulnerability AssessmentAI
| Exploitation | Exploitation requires all three of: (1) the target kernel runs on IBM s390/zSeries hardware - x86, ARM, and all other architectures are completely unaffected; (2) the running kernel binary was compiled with GNU binutils earlier than 2.39 (binutils 2.30 through 2.38 are within Linux's supported build range, so this configuration legitimately exists in enterprise distributions); and (3) a local attacker with at minimum unprivileged process execution can trigger the per-CPU path and induce CPU migration during an interrupted per-CPU sequence. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 score of 7.0 (AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H) is calibrated correctly - AC:H reflects the double precondition of s390 hardware plus an older-binutils kernel build, which substantially limits the exploitable population. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor-released patch: Linux 7.2.4 and 7.3-rc1 (upstream stable commits 91770b08a120967077ae78600612f18bc5ee3caf and 101782f8945a125044347312d74d488c05741c4a at git.kernel.org). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all s390/zSeries systems in production running kernel 7.2 lineage compiled with binutils earlier than 2.39 and flag them for priority patching. …
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