{"api_version":"1","generated_at":"2026-04-20T14:03:35+00:00","cve":"CVE-2026-31429","urls":{"html":"https://cve.report/CVE-2026-31429","api":"https://cve.report/api/cve/CVE-2026-31429.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-31429","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-31429"},"summary":{"title":"net: skb: fix cross-cache free of KFENCE-allocated skb head","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: skb: fix cross-cache free of KFENCE-allocated skb head\n\nSKB_SMALL_HEAD_CACHE_SIZE is intentionally set to a non-power-of-2\nvalue (e.g. 704 on x86_64) to avoid collisions with generic kmalloc\nbucket sizes. This ensures that skb_kfree_head() can reliably use\nskb_end_offset to distinguish skb heads allocated from\nskb_small_head_cache vs. generic kmalloc caches.\n\nHowever, when KFENCE is enabled, kfence_ksize() returns the exact\nrequested allocation size instead of the slab bucket size. If a caller\n(e.g. bpf_test_init) allocates skb head data via kzalloc() and the\nrequested size happens to equal SKB_SMALL_HEAD_CACHE_SIZE, then\nslab_build_skb() -> ksize() returns that exact value. After subtracting\nskb_shared_info overhead, skb_end_offset ends up matching\nSKB_SMALL_HEAD_HEADROOM, causing skb_kfree_head() to incorrectly free\nthe object to skb_small_head_cache instead of back to the original\nkmalloc cache, resulting in a slab cross-cache free:\n\n  kmem_cache_free(skbuff_small_head): Wrong slab cache. Expected\n  skbuff_small_head but got kmalloc-1k\n\nFix this by always calling kfree(head) in skb_kfree_head(). This keeps\nthe free path generic and avoids allocator-specific misclassification\nfor KFENCE objects.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-04-20 10:16:16","updated_at":"2026-04-20 10:16:16"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/474e00b935db250cac320d10c1d3cf4e44b46721","name":"https://git.kernel.org/stable/c/474e00b935db250cac320d10c1d3cf4e44b46721","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516","name":"https://git.kernel.org/stable/c/0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/60313768a8edc7094435975587c00c2d7b834083","name":"https://git.kernel.org/stable/c/60313768a8edc7094435975587c00c2d7b834083","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/2d64618ea846d8d033477311f805ca487d6a6696","name":"https://git.kernel.org/stable/c/2d64618ea846d8d033477311f805ca487d6a6696","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-31429","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31429","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected bf9f1baa279f0758dc2297080360c5a616843927 60313768a8edc7094435975587c00c2d7b834083 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected bf9f1baa279f0758dc2297080360c5a616843927 2d64618ea846d8d033477311f805ca487d6a6696 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected bf9f1baa279f0758dc2297080360c5a616843927 474e00b935db250cac320d10c1d3cf4e44b46721 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected bf9f1baa279f0758dc2297080360c5a616843927 0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.3","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.3 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.82 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.23 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19.13 6.19.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/core/skbuff.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"60313768a8edc7094435975587c00c2d7b834083","status":"affected","version":"bf9f1baa279f0758dc2297080360c5a616843927","versionType":"git"},{"lessThan":"2d64618ea846d8d033477311f805ca487d6a6696","status":"affected","version":"bf9f1baa279f0758dc2297080360c5a616843927","versionType":"git"},{"lessThan":"474e00b935db250cac320d10c1d3cf4e44b46721","status":"affected","version":"bf9f1baa279f0758dc2297080360c5a616843927","versionType":"git"},{"lessThan":"0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516","status":"affected","version":"bf9f1baa279f0758dc2297080360c5a616843927","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/core/skbuff.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.3"},{"lessThan":"6.3","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.82","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.23","versionType":"semver"},{"lessThanOrEqual":"6.19.*","status":"unaffected","version":"6.19.13","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.0","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.82","versionStartIncluding":"6.3","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.23","versionStartIncluding":"6.3","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.19.13","versionStartIncluding":"6.3","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0","versionStartIncluding":"6.3","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: skb: fix cross-cache free of KFENCE-allocated skb head\n\nSKB_SMALL_HEAD_CACHE_SIZE is intentionally set to a non-power-of-2\nvalue (e.g. 704 on x86_64) to avoid collisions with generic kmalloc\nbucket sizes. This ensures that skb_kfree_head() can reliably use\nskb_end_offset to distinguish skb heads allocated from\nskb_small_head_cache vs. generic kmalloc caches.\n\nHowever, when KFENCE is enabled, kfence_ksize() returns the exact\nrequested allocation size instead of the slab bucket size. If a caller\n(e.g. bpf_test_init) allocates skb head data via kzalloc() and the\nrequested size happens to equal SKB_SMALL_HEAD_CACHE_SIZE, then\nslab_build_skb() -> ksize() returns that exact value. After subtracting\nskb_shared_info overhead, skb_end_offset ends up matching\nSKB_SMALL_HEAD_HEADROOM, causing skb_kfree_head() to incorrectly free\nthe object to skb_small_head_cache instead of back to the original\nkmalloc cache, resulting in a slab cross-cache free:\n\n  kmem_cache_free(skbuff_small_head): Wrong slab cache. Expected\n  skbuff_small_head but got kmalloc-1k\n\nFix this by always calling kfree(head) in skb_kfree_head(). This keeps\nthe free path generic and avoids allocator-specific misclassification\nfor KFENCE objects."}],"providerMetadata":{"dateUpdated":"2026-04-20T09:43:03.194Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/60313768a8edc7094435975587c00c2d7b834083"},{"url":"https://git.kernel.org/stable/c/2d64618ea846d8d033477311f805ca487d6a6696"},{"url":"https://git.kernel.org/stable/c/474e00b935db250cac320d10c1d3cf4e44b46721"},{"url":"https://git.kernel.org/stable/c/0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516"}],"title":"net: skb: fix cross-cache free of KFENCE-allocated skb head","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-31429","datePublished":"2026-04-20T09:43:03.194Z","dateReserved":"2026-03-09T15:48:24.089Z","dateUpdated":"2026-04-20T09:43:03.194Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-04-20 10:16:16","lastModifiedDate":"2026-04-20 10:16:16","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"31429","Ordinal":"1","Title":"net: skb: fix cross-cache free of KFENCE-allocated skb head","CVE":"CVE-2026-31429","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"31429","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: skb: fix cross-cache free of KFENCE-allocated skb head\n\nSKB_SMALL_HEAD_CACHE_SIZE is intentionally set to a non-power-of-2\nvalue (e.g. 704 on x86_64) to avoid collisions with generic kmalloc\nbucket sizes. This ensures that skb_kfree_head() can reliably use\nskb_end_offset to distinguish skb heads allocated from\nskb_small_head_cache vs. generic kmalloc caches.\n\nHowever, when KFENCE is enabled, kfence_ksize() returns the exact\nrequested allocation size instead of the slab bucket size. If a caller\n(e.g. bpf_test_init) allocates skb head data via kzalloc() and the\nrequested size happens to equal SKB_SMALL_HEAD_CACHE_SIZE, then\nslab_build_skb() -> ksize() returns that exact value. After subtracting\nskb_shared_info overhead, skb_end_offset ends up matching\nSKB_SMALL_HEAD_HEADROOM, causing skb_kfree_head() to incorrectly free\nthe object to skb_small_head_cache instead of back to the original\nkmalloc cache, resulting in a slab cross-cache free:\n\n  kmem_cache_free(skbuff_small_head): Wrong slab cache. Expected\n  skbuff_small_head but got kmalloc-1k\n\nFix this by always calling kfree(head) in skb_kfree_head(). This keeps\nthe free path generic and avoids allocator-specific misclassification\nfor KFENCE objects.","Type":"Description","Title":"net: skb: fix cross-cache free of KFENCE-allocated skb head"}]}}}