Linux hwe edge: In the Linux kernel, the following vulnerability has been resolved: net: skb: fix cross-cache free of KFENCE-allocated skb head… (CVE-2026-31429)
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.
AI Analysis
Technical Summary
The Linux kernel vulnerability CVE-2026-31429 involves the network subsystem's skb (socket buffer) memory management when KFENCE (Kernel Electric Fence) is enabled. KFENCE returns the exact requested allocation size rather than the slab bucket size, which causes skb_kfree_head() to misidentify the cache to which the skb head should be freed. Specifically, when an skb head allocated via kzalloc() matches SKB_SMALL_HEAD_CACHE_SIZE, skb_end_offset matches SKB_SMALL_HEAD_HEADROOM, leading to freeing the object to the wrong cache. This results in a use-after-free condition, potentially causing system instability or crashes. The issue affects Linux kernel versions prior to 6.8.0-1064.72~22.04.1 and other related builds as listed. The vulnerability has been addressed in updated kernel releases. The vendor advisory from Ubuntu confirms the availability of patches and recommends updating and rebooting systems. The advisory also notes an ABI change requiring recompilation of third-party kernel modules.
Potential Impact
This vulnerability can cause a use-after-free condition in the Linux kernel's networking stack, potentially leading to system crashes or instability (availability impact). There is no indication of confidentiality or integrity impact. The CVSS score of 5.5 reflects a medium severity with local attack vector, low complexity, requiring low privileges, no user interaction, and impact limited to availability.
Mitigation Recommendations
A patch is available for this vulnerability. Users should update their Linux kernel to the fixed versions as specified by their distribution vendor (e.g., Ubuntu) and reboot the system to apply the changes. Due to an ABI change in the kernel update, recompilation and reinstallation of all third-party kernel modules are required. Follow vendor instructions carefully to ensure full remediation.
Linux hwe edge: In the Linux kernel, the following vulnerability has been resolved: net: skb: fix cross-cache free of KFENCE-allocated skb head… (CVE-2026-31429)
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 v3.1
Score 5.5medium
Affected software
pkg:deb/ubuntu/[email protected]~16.04.1?arch=source&distro=xenialpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.2?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.1?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.1?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.1?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.2?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~18.04.1?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.2?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]+cvm1.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.3?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~20.04.1?arch=source&distro=focalpkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.2?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.2.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]~22.04.2?arch=source&distro=realtime/jammypkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=bluefield/noblepkg:deb/ubuntu/[email protected]+fips1?arch=source&distro=fips-updates/noblepkg:deb/ubuntu/[email protected]+fips1?arch=source&distro=fips-updates/noblepkg:deb/ubuntu/[email protected]+fips1?arch=source&distro=fips-updates/noblepkg:deb/ubuntu/[email protected]+fips1?arch=source&distro=fips-updates/noblepkg:deb/ubuntu/[email protected]?arch=source&distro=realtime/noblepkg:deb/ubuntu/[email protected]?arch=source&distro=realtime/noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=realtime/noblepkg:deb/ubuntu/[email protected]~24.04.1?arch=source&distro=realtime/noblepkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=resoluteRun on your own infrastructure? 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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel vulnerability CVE-2026-31429 involves the network subsystem's skb (socket buffer) memory management when KFENCE (Kernel Electric Fence) is enabled. KFENCE returns the exact requested allocation size rather than the slab bucket size, which causes skb_kfree_head() to misidentify the cache to which the skb head should be freed. Specifically, when an skb head allocated via kzalloc() matches SKB_SMALL_HEAD_CACHE_SIZE, skb_end_offset matches SKB_SMALL_HEAD_HEADROOM, leading to freeing the object to the wrong cache. This results in a use-after-free condition, potentially causing system instability or crashes. The issue affects Linux kernel versions prior to 6.8.0-1064.72~22.04.1 and other related builds as listed. The vulnerability has been addressed in updated kernel releases. The vendor advisory from Ubuntu confirms the availability of patches and recommends updating and rebooting systems. The advisory also notes an ABI change requiring recompilation of third-party kernel modules.
Potential Impact
This vulnerability can cause a use-after-free condition in the Linux kernel's networking stack, potentially leading to system crashes or instability (availability impact). There is no indication of confidentiality or integrity impact. The CVSS score of 5.5 reflects a medium severity with local attack vector, low complexity, requiring low privileges, no user interaction, and impact limited to availability.
Mitigation Recommendations
A patch is available for this vulnerability. Users should update their Linux kernel to the fixed versions as specified by their distribution vendor (e.g., Ubuntu) and reboot the system to apply the changes. Due to an ABI change in the kernel update, recompilation and reinstallation of all third-party kernel modules are required. Follow vendor instructions carefully to ensure full remediation.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-31429
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:16.04:LTS","Ubuntu:18.04:LTS","Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:Pro:Realtime:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:Nvidia-BlueField:24.04:LTS","Ubuntu:Pro:FIPS-updates:24.04:LTS","Ubuntu:Pro:Realtime:24.04:LTS","Ubuntu:25.10","Ubuntu:26.04:LTS"]
- Cvss Version
- 3.1
Threat ID: 6a5b624d2d1edb114c88baff
Added to database: 07/18/2026, 11:23:57 UTC
Last enriched: 08/01/2026, 05:54:22 UTC
Last updated: 09/14/2026, 22:01:33 UTC
Views: 22
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