CVE-2025-40008
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-20

Last updated on: 2025-10-21

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: kmsan: fix out-of-bounds access to shadow memory Running sha224_kunit on a KMSAN-enabled kernel results in a crash in kmsan_internal_set_shadow_origin(): BUG: unable to handle page fault for address: ffffbc3840291000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 1810067 P4D 1810067 PUD 192d067 PMD 3c17067 PTE 0 Oops: 0000 [#1] SMP NOPTI CPU: 0 UID: 0 PID: 81 Comm: kunit_try_catch Tainted: G N 6.17.0-rc3 #10 PREEMPT(voluntary) Tainted: [N]=TEST Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 RIP: 0010:kmsan_internal_set_shadow_origin+0x91/0x100 [...] Call Trace: <TASK> __msan_memset+0xee/0x1a0 sha224_final+0x9e/0x350 test_hash_buffer_overruns+0x46f/0x5f0 ? kmsan_get_shadow_origin_ptr+0x46/0xa0 ? __pfx_test_hash_buffer_overruns+0x10/0x10 kunit_try_run_case+0x198/0xa00 This occurs when memset() is called on a buffer that is not 4-byte aligned and extends to the end of a guard page, i.e. the next page is unmapped. The bug is that the loop at the end of kmsan_internal_set_shadow_origin() accesses the wrong shadow memory bytes when the address is not 4-byte aligned. Since each 4 bytes are associated with an origin, it rounds the address and size so that it can access all the origins that contain the buffer. However, when it checks the corresponding shadow bytes for a particular origin, it incorrectly uses the original unrounded shadow address. This results in reads from shadow memory beyond the end of the buffer's shadow memory, which crashes when that memory is not mapped. To fix this, correctly align the shadow address before accessing the 4 shadow bytes corresponding to each origin.
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Meta Information
Published
2025-10-20
Last Modified
2025-10-21
Generated
2026-05-06
AI Q&A
2025-10-20
EPSS Evaluated
2026-05-05
NVD
CVE-2025-40008
EUVD
EUVD-2025-35072
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux kernel 6.17.0-rc3
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a bug in the Linux kernel's Kernel Memory Sanitizer (KMSAN) related to out-of-bounds access to shadow memory. Specifically, when a buffer that is not 4-byte aligned and extends to the end of a guard page is processed, the kmsan_internal_set_shadow_origin() function accesses shadow memory beyond the buffer's allocated shadow memory. This happens because the function incorrectly uses the original unrounded shadow address when checking shadow bytes, leading to reads from unmapped memory and causing a kernel crash.


How can this vulnerability impact me? :

This vulnerability can cause the Linux kernel to crash (kernel panic) when running certain operations, such as sha224_kunit on a KMSAN-enabled kernel. The crash occurs due to out-of-bounds memory access in the kernel, which can lead to system instability or denial of service.


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