CVE-2025-68179 s390: Disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
Enabling HugeTLB Vmemmap Optimization on s390 causes kernel crashes due to improper TLB flushing, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-68179?
CVE-2025-68179 is a high-severity denial of service vulnerability in Linux, published on 16 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
s390: Disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
As reported by Luiz Capitulino enabling HVO on s390 leads to reproducible crashes. The problem is that kernel page tables are modified without flushing corresponding TLB entries.
Even if it looks like the empty flush_tlb_all() implementation on s390 is the problem, it is actually a different problem: on s390 it is not allowed to replace an active/valid page table entry with another valid page table entry without the detour over an invalid entry. A direct replacement may lead to random crashes and/or data corruption.
In order to invalidate an entry special instructions have to be used (e.g. ipte or idte). Alternatively there are also special instructions available which allow to replace a valid entry with a different valid entry (e.g. crdte or cspg).
Given that the HVO code currently does not provide the hooks to allow for an implementation which is compliant with the s390 architecture requirements, disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP again, which is basically a revert of the original patch which enabled it.
Which versions are affected by CVE-2025-68179?
How do I fix CVE-2025-68179?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-68179 being exploited?
There is no known exploitation of CVE-2025-68179 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-68179, DEBIAN-CVE-2025-68179, GHSA-2v94-v9cc-qp7h, ROOT-OS-DEBIAN-13-CVE-2025-68179, ROOT-OS-UBUNTU-2404-CVE-2025-68179, UBUNTU-CVE-2025-68179.