Executive brief
A vulnerability in the Linux kernel's memory management for x86 systems can cause the operating system to crash during startup. This occurs when the system has very low available contiguous memory, leading the kernel to incorrectly handle memory allocation failures. An exploit of this issue results in a complete system outage (denial of service), impacting business operations and service availability.
Technical details
A vulnerability exists in the x86/mm subsystem of the Linux kernel due to a missing return value check for memblock_phys_alloc_range() in arch/x86/mm/init.c. When the kernel is configured with CONFIG_PHYSICAL_START=0x100000 and there is less than 4 MiB of contiguous free memory, the function returns 0 on failure. The kernel subsequently passes this 0 value to memblock_phys_free(), causing it to incorrectly release the first 4 MiB of physical memory, leading to a system crash. This is a local denial-of-service vulnerability that occurs during the early boot/initialization phase. Patches have been released across multiple stable kernel branches to implement proper error handling and graceful failure.
Affected products
- Linux Linux Kernel up to 6.1.141, 6.2 to 6.6.93, 6.7 to 6.12.31, 6.13 to 6.14.9
Timeline
- 2024-11-15: other: Vulnerability fixed in source code
- 2025-06-18: advisory: CVE published by kernel.org
- 2025-10-01: advisory: Debian LTS advisory published
References
- https://git.kernel.org/stable/c/631ca8909fd5c62b9fda9edda93924311a78a9c4
- https://git.kernel.org/stable/c/8c18c904d301ffeb33b071eadc55cd6131e1e9be
- https://git.kernel.org/stable/c/bffd5f2815c5234d609725cd0dc2f4bc5de2fc67
- https://git.kernel.org/stable/c/c6f2694c580c27dca0cf7546ee9b4bfa6b940e38
- https://git.kernel.org/stable/c/dde4800d2b0f68b945fd81d4fc2d4a10ae25f743
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html