CVE-2026-31429
- Source
- https://cve.org/CVERecord?id=CVE-2026-31429
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31429.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2026-31429
- Downstream
- Related
- Published
- 2026-04-20T09:43:03Z
- Modified
- 2026-08-12T03:51:34Z
- Summary
- net: skb: fix cross-cache free of KFENCE-allocated skb head
- Details
-
In the Linux kernel, the following vulnerability has been resolved:
net: skb: fix cross-cache free of KFENCE-allocated skb head
SKB_SMALL_HEAD_CACHE_SIZE is intentionally set to a non-power-of-2 value (e.g. 704 on x86_64) to avoid collisions with generic kmalloc bucket sizes. This ensures that skb_kfree_head() can reliably use skb_end_offset to distinguish skb heads allocated from skb_small_head_cache vs. generic kmalloc caches.
However, when KFENCE is enabled, kfence_ksize() returns the exact requested allocation size instead of the slab bucket size. If a caller (e.g. bpf_test_init) allocates skb head data via kzalloc() and the requested size happens to equal SKB_SMALL_HEAD_CACHE_SIZE, then slab_build_skb() -> ksize() returns that exact value. After subtracting skb_shared_info overhead, skb_end_offset ends up matching SKB_SMALL_HEAD_HEADROOM, causing skb_kfree_head() to incorrectly free the object to skb_small_head_cache instead of back to the original kmalloc cache, resulting in a slab cross-cache free:
kmem_cache_free(skbuff_small_head): Wrong slab cache. Expected skbuff_small_head but got kmalloc-1k
Fix this by always calling kfree(head) in skb_kfree_head(). This keeps the free path generic and avoids allocator-specific misclassification for KFENCE objects.
- Database specific
{ "cna_assigner": "Linux", "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31429.json" }- References
-
- https://git.kernel.org/stable/c/0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516
- https://git.kernel.org/stable/c/128b03ccb2582a643983a48a37fda58df80edbde
- https://git.kernel.org/stable/c/2d64618ea846d8d033477311f805ca487d6a6696
- https://git.kernel.org/stable/c/474e00b935db250cac320d10c1d3cf4e44b46721
- https://git.kernel.org/stable/c/60313768a8edc7094435975587c00c2d7b834083
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31429.json
- https://nvd.nist.gov/vuln/detail/CVE-2026-31429
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Affected packages
Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Affected ranges
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introducedbf9f1baa279f0758dc2297080360c5a616843927Fixed128b03ccb2582a643983a48a37fda58df80edbdeFixed60313768a8edc7094435975587c00c2d7b834083Fixed2d64618ea846d8d033477311f805ca487d6a6696Fixed474e00b935db250cac320d10c1d3cf4e44b46721Fixed0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516