CVE-2026-45990
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk8th percentile - higher than 8% of all known CVEs
Summary
A vulnerability has been identified in the Linux kernel's krealloc() function that may lead to data loss and buffer overflow during object resizing. These issues arise from improper size management during NUMA migration and when shrinking objects.
Risk Assessment
Organizations may be exposed to data loss and potential system crashes due to memory allocation errors. Exploitation of this vulnerability could lead to unexpected application behavior.
Recommendation
It is recommended to update the Linux kernel to the latest version to mitigate this vulnerability. Additionally, monitor systems for any abnormal behavior related to memory allocation.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: slub: fix data loss and overflow in krealloc() Commit 2cd8231796b5 ("mm/slub: allow to set node and align in k[v]realloc") introduced the ability to force a reallocation if the original object does not satisfy new alignment or NUMA node, even when the object is being shrunk. This introduced two bugs in the reallocation fallback path: 1. Data loss during NUMA migration: The jump to 'alloc_new' happens before 'ks' and 'orig_size' are initialized. As a result, the memcpy() in the 'alloc_new' block would copy 0 bytes into the new allocation. 2. Buffer overflow during shrinking: When shrinking an object while forcing a new alignment, 'new_size' is smaller than the old size. However, the memcpy() used the old size ('orig_size ?: ks'), leading to an out-of-bounds write. The same overflow bug exists in the kvrealloc() fallback path, where the old bucket size ksize(p) is copied into the new buffer without being bounded by the new size. A simple reproducer: // e.g. add to lkdtm as KREALLOC_SHRINK_OVERFLOW while (1) { void *p = kmalloc(128, GFP_KERNEL); p = krealloc_node_align(p, 64, 256, GFP_KERNEL, NUMA_NO_NODE); kfree(p); } demonstrates the issue: ================================================================== BUG: KFENCE: out-of-bounds write in memcpy_orig+0x68/0x130 Out-of-bounds write at 0xffff8883ad757038 (120B right of kfence-#47): memcpy_orig+0x68/0x130 krealloc_node_align_noprof+0x1c8/0x340 lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm] lkdtm_do_action+0x3a/0x60 [lkdtm] ... kfence-#47: 0xffff8883ad756fc0-0xffff8883ad756fff, size=64, cache=kmalloc-64 allocated by task 316 on cpu 7 at 97.680481s (0.021813s ago): krealloc_node_align_noprof+0x19c/0x340 lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm] lkdtm_do_action+0x3a/0x60 [lkdtm] ... ================================================================== Fix it by moving the old size calculation to the top of __do_krealloc() and bounding all copy lengths by the new allocation size.