Summary
In the Linux kernel, the following vulnerability has been resolved: kmsan: fix out-of-bounds...
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.
Impact
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2025-40008? CVE-2025-40008 is a unknown-severity security vulnerability. No fixed version is listed yet.
- Is there a fix for CVE-2025-40008? No fixed version is listed for CVE-2025-40008 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2025-40008 exploitable, and should I be worried? Whether CVE-2025-40008 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-40008 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.