EUVD-2026-39893
GHSA-24wq-6x4v-q3fv
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Reliable triggering requires arm64 hardware plus 4K page granule configuration plus the specific vulnerable commit window, warranting AC:H over the NVD-assigned AC:L.
Primary rating from NVD.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionNVD
In the Linux kernel, the following vulnerability has been resolved:
arm64: Reserve an extra page for early kernel mapping
The final part of [data, end) segment may overflow into the next page of init_pg_end[1] which is the gap page before early_init_stack[2]:
[1] crash_arm64_v9.0.1> vtop ffffffed00601000 VIRTUAL PHYSICAL ffffffed00601000 83401000
PAGE DIRECTORY: ffffffecffd62000 PGD: ffffffecffd62da0 => 10000000833fb003 PMD: ffffff80033fb018 => 10000000833fe003 PTE: ffffff80033fe008 => 68000083401f03 PAGE: 83401000
PTE PHYSICAL FLAGS 68000083401f03 83401000 (VALID|SHARED|AF|NG|PXN|UXN)
PAGE PHYSICAL MAPPING INDEX CNT FLAGS fffffffec00d0040 83401000 0 0 1 4000 reserved
[2] ffffffed002c8000 (r) __pi__data ffffffed0054e000 (d) __pi___bss_start ffffffed005f5000 (b) __pi_init_pg_dir ffffffed005fe000 (b) __pi_init_pg_end ffffffed005ff000 (B) early_init_stack ffffffed00608000 (b) __pi__end
For 4K pages, the early kernel mapping may use 2MB block entries but the kernel segments are only 64KB aligned. Segment boundaries that fall within a 2MB block therefore require a PTE table so that different attributes can be applied on either side of the boundary.
KERNEL_SEGMENT_COUNT still correctly counts the five permanent kernel VMAs registered by declare_kernel_vmas(). However, since commit 5973a62efa34 ("arm64: map [_text, _stext) virtual address range non-executable+read-only"), the early mapper also maps [_text, _stext) separately from [_stext, _etext). This adds one more early-only split and can require one more page-table page than the existing EARLY_SEGMENT_EXTRA_PAGES allowance reserves.
Increase the 4K-page early mapping allowance by one page to cover that additional split.
[catalin.marinas@arm.com: rewrote part of the commit log] [catalin.marinas@arm.com: expanded the code comment]
AnalysisAI
Memory corruption in the arm64 early kernel mapping on Linux allows a local low-privileged user to cause a kernel panic through an off-by-one page-table allocation error introduced since commit 5973a62efa34. Affected systems running 4K page granule on arm64 hardware may have the [data, end) segment overflow into the guard gap page before early_init_stack, corrupting critical early initialization memory. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires local access with low privileges (CVSS PR:L, AV:L) on an arm64 (AArch64) system. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | CVSS 5.5 (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) reflects a local, low-complexity DoS with no confidentiality or integrity impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | On an arm64 server or embedded device running a 4K page granule Linux kernel in the affected version range, the early mapping phase allocates one fewer page-table page than required for the extra [_text, _stext) split. The tail of the kernel data segment overflows into the guard gap page before early_init_stack, corrupting that page's content. … |
| Remediation | Upgrade to a patched kernel version: 6.12.91 or later for the 6.12.x stable series, 6.18 or later for the 6.17.x series, or 7.0.10 or later for the 7.0.x series. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-674 – Uncontrolled Recursion
View allSame technique Denial Of Service
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External POC / Exploit Code
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