CVE-2025-39904
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-01

Last updated on: 2025-12-12

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: arm64: kexec: initialize kexec_buf struct in load_other_segments() Patch series "kexec: Fix invalid field access". The kexec_buf structure was previously declared without initialization. commit bf454ec31add ("kexec_file: allow to place kexec_buf randomly") added a field that is always read but not consistently populated by all architectures. This un-initialized field will contain garbage. This is also triggering a UBSAN warning when the uninitialized data was accessed: ------------[ cut here ]------------ UBSAN: invalid-load in ./include/linux/kexec.h:210:10 load of value 252 is not a valid value for type '_Bool' Zero-initializing kexec_buf at declaration ensures all fields are cleanly set, preventing future instances of uninitialized memory being used. An initial fix was already landed for arm64[0], and this patchset fixes the problem on the remaining arm64 code and on riscv, as raised by Mark. Discussions about this problem could be found at[1][2]. This patch (of 3): The kexec_buf structure was previously declared without initialization. commit bf454ec31add ("kexec_file: allow to place kexec_buf randomly") added a field that is always read but not consistently populated by all architectures. This un-initialized field will contain garbage. This is also triggering a UBSAN warning when the uninitialized data was accessed: ------------[ cut here ]------------ UBSAN: invalid-load in ./include/linux/kexec.h:210:10 load of value 252 is not a valid value for type '_Bool' Zero-initializing kexec_buf at declaration ensures all fields are cleanly set, preventing future instances of uninitialized memory being used.
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Meta Information
Published
2025-10-01
Last Modified
2025-12-12
Generated
2026-06-16
AI Q&A
2025-10-01
EPSS Evaluated
2026-06-15
NVD
CVE-2025-39904
Affected Vendors & Products
Showing 6 associated CPEs
Vendor Product Version / Range
linux linux_kernel From 6.16 (inc) to 6.16.8 (exc)
linux linux_kernel 6.17
linux linux_kernel 6.17
linux linux_kernel 6.17
linux linux_kernel 6.17
linux linux_kernel 6.17
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-908 The product uses or accesses a resource that has not been initialized.
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Executive Summary

This vulnerability involves the Linux kernel's kexec_buf structure, which was declared without proper initialization. A recent commit added a field that is always read but not consistently set by all architectures, causing the field to contain uninitialized (garbage) data. This leads to invalid memory access and triggers UBSAN warnings. The fix zero-initializes the kexec_buf structure at declaration to ensure all fields are cleanly set and prevent use of uninitialized memory.

Impact Analysis

The impact of this vulnerability is that uninitialized memory may be accessed, which can cause undefined behavior, potential crashes, or security issues related to invalid memory reads in the Linux kernel's kexec functionality. This could affect system stability or security on affected architectures like arm64 and riscv.

Mitigation Strategies

Apply the patch that zero-initializes the kexec_buf structure at declaration to ensure all fields are cleanly set, preventing uninitialized memory usage. This fix has been applied to arm64 and riscv architectures as described in the patch series "kexec: Fix invalid field access".

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