CVE-2026-72043
HighCVSS 7.1Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
In the Linux kernel on LoongArch architecture, a vulnerability was found related to missing dirty page tracking in pte_wrprotect() and pmd_wrprotect(). When hardware page table walker (PTW) is enabled, it may set _PAGE_DIRTY without setting _PAGE_MODIFIED, leading to loss of dirty information during copy-on-write (fork). As a result, a page may be considered clean and freed without writeback, causing data corruption.
Risk Assessment
The organization is exposed to data corruption on systems with LoongArch processors, especially under memory pressure and fork/madvise operations. This can lead to data integrity loss, application crashes, or unpredictable system behavior.
Recommendation
It is recommended to immediately apply the official Linux kernel patch for CVE-2026-72043, which propagates the _PAGE_DIRTY bit to _PAGE_MODIFIED in pte_wrprotect() and pmd_wrprotect(). Also monitor for new kernel releases from your distribution.
Other vulnerabilities in Linux kernel
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- CVE-2026-99258Unknown
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- CVE-2026-99257Unknown
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- CVE-2026-99256Unknown
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- CVE-2026-99251Unknown
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- CVE-2026-99250Unknown
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- CVE-2026-99249Unknown
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- CVE-2026-99248Unknown
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- CVE-2026-99247Unknown
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: LoongArch: Fix missing dirty page tracking in {pte,pmd}_wrprotect() When hardware page table walker (PTW) is enabled on LoongArch, the CPU may set _PAGE_DIRTY directly in the page table entry during a write TLB miss, without going through the software TLB store handler. The software TLB store handler (tlbex.S:254) sets both _PAGE_DIRTY and_PAGE_MODIFIED together: ori t0, t0, (_PAGE_VALID | _PAGE_DIRTY | _PAGE_MODIFIED) Since hardware PTW only sets _PAGE_DIRTY, the software-only bit, i.e. _PAGE_MODIFIED is left unchanged. This creates a window where a PTE has _PAGE_DIRTY set (hardware knows the page is dirty) but _PAGE_MODIFIED clear (software is unaware). When fork()/clone() triggers copy-on-write, __copy_present_ptes() calls pte_wrprotect(), which unconditionally clears both the _PAGE_WRITE and _PAGE_DIRTY bits: pte_val(pte) &= ~(_PAGE_WRITE | _PAGE_DIRTY); Since _PAGE_MODIFIED was never set, the dirtiness information is lost completely. Subsequently, when memory pressure triggers page reclaim, page_mkclean() / try_to_unmap() sees the page as clean (i.e. pte_dirty() returns false) and the page may be freed without writeback, causing data corruption. Fix this by propagating the _PAGE_DIRTY bit to the _PAGE_MODIFIED bit in both pte_wrprotect() and pmd_wrprotect() before clearing writeable bits: if (pte_val(pte) & _PAGE_DIRTY) pte_val(pte) |= _PAGE_MODIFIED; The pmd_wrprotect() fix handles the CONFIG_TRANSPARENT_HUGEPAGE case, where pmd entries need the same treatment. This ensures the software dirty tracking bit (checked by pte_dirty() and pmd_dirty(), which read both the _PAGE_DIRTY and _PAGE_MODIFIED bits) is preserved across fork COW write-protection. The issue was found by the LTP madvise09 test case, which exercises page reclaim after "madvise(MADV_FREE), write and fork" operation sequence on private anonymous mappings.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

