Kernel crash via writable PTE batch restoration
Published Apr 3, 2026 · Updated Apr 3, 2026
Reachable assertion in Linux Kernel allows local users to crash the kernel by creating mixed-permission lazyfree page-table batches. folio_unmap_pte_batch restores a batch containing writable and non-writable PTEs as entirely writable, violating anonymous-memory copy-on-write semantics and firing the page_table_check_set BUG_ON assertion. Exploitation requires low-privilege local access, 64K multi-size transparent huge pages, VMA splitting and merging, MADV_FREE, and memory reclaim; the demonstrated consequence is a kernel crash.
Summary
What happened
Reachable assertion in Linux Kernel allows local users to crash the kernel by creating mixed-permission lazyfree page-table batches. folio_unmap_pte_batch restores a batch containing writable and non-writable PTEs as entirely writable, violating anonymous-memory copy-on-write semantics and firing the page_table_check_set BUG_ON assertion. Exploitation requires low-privilege local access, 64K multi-size transparent huge pages, VMA splitting and merging, MADV_FREE, and memory reclaim; the demonstrated consequence is a kernel crash.
The record
- CVE
- CVE-2026-31398
- Published
- Apr 3, 2026
- Updated
- Apr 3, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- CWE-617, T1499.004
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 3, 2026CVE publishedPublication date reported by the CVE source.
- Apr 3, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=354dffd29575cdf13154e8fb787322354aa9efc4 <29f40594a28114b9a9bc87f6cf7bbee9609628f2
- Affected versionversion=354dffd29575cdf13154e8fb787322354aa9efc4 <99888a4f340ca8e839a0524556bd4db76d63f4e0
- Affected versionversion=354dffd29575cdf13154e8fb787322354aa9efc4 <a0911ccdba41b0871abbf8412857bafedec3dbe1
- Affected versionversion=6.15
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo