# CVE-2026-45990: linux: In the Linux kernel, the following vulnerability has been resolved: slub: fix data loss and overflow in krealloc()... CVE-2026-45990 is fixed in 19 products on 1 platform, first by ALAS2023-2026-1754, released May 25, 2026. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2026-45990 - Priority: Routine - CVSS: 5.5 (medium) - EPSS: 0.0013 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: May 25, 2026 ## Description 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. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | bpftool6.18 amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | bpftool6.18-debuginfo amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel-livepatch-6.18.30-61.116 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18 amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18-debuginfo amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18-debuginfo-common-aarch64 amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18-debuginfo-common-x86_64 amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18-devel amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18-headers amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18-modules-extra amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18-modules-extra-common amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18-tools amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18-tools-debuginfo amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | kernel6.18-tools-devel amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | linux Debian 14 | 7.0.4-1 | [DEBIAN-CVE-2026-45990](https://patchblox.com/security/data/fix/linux/debian-cve-2026-45990.md) | May 27, 2026 | | Linux | perf6.18 amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | perf6.18-debuginfo amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | python3-perf6.18 amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | | Linux | python3-perf6.18-debuginfo amzn 2023 | 1:6.18.30-61.116.amzn2023 | [ALAS2023-2026-1754](https://patchblox.com/security/data/fix/linux/alas2023-2026-1754.md) | May 25, 2026 | --- Data as of 2026-11-08T19:12:23Z UTC. 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