CVE-2026-31429

MEDIUM EPSS 17.2%
Published Apr 20, 20262mo ago · Modified Jun 17, 20261w ago
5.5 CVSS 3.1
Medium
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Published Apr 20, 2026 2mo ago
Last Modified Jun 17, 2026 1w ago

Description

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.

CVSS Details

Base Score
5.5
Exploitability
1.8
Impact
3.6
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Vector Local
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability High

Threat Intelligence

EPSS Exploit Probability
17.2% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-401

Affected Products 11

VendorProductVersionRange
linuxlinux_kernel*≥6.3  –  <6.6.136
linuxlinux_kernel*≥6.7  –  <6.12.82
linuxlinux_kernel*≥6.13  –  <6.18.23
linuxlinux_kernel*≥6.19  –  <6.19.13
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any

References 5

  • git.kernel.org https://git.kernel.org/stable/c/0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/128b03ccb2582a643983a48a37fda58df80edbde
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/2d64618ea846d8d033477311f805ca487d6a6696
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/474e00b935db250cac320d10c1d3cf4e44b46721
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/60313768a8edc7094435975587c00c2d7b834083
    Patch

Remediation

  • git.kernel.org https://git.kernel.org/stable/c/0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/128b03ccb2582a643983a48a37fda58df80edbde
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/2d64618ea846d8d033477311f805ca487d6a6696
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/474e00b935db250cac320d10c1d3cf4e44b46721
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/60313768a8edc7094435975587c00c2d7b834083
    Patch