vxlan: use one headroom snapshot for neighbour replies
In the Linux kernel, the following vulnerability has been resolved: vxlan: use one headroom snapshot for neighbour replies vxlan_na_create() samples LL_RESERVED_SPACE() to size the reply skb and then samples it again to reserve headroom. A concurrent vxlan_changelink() can update needed_headroom between the two reads, creating a TOCTOU race. The second value can exceed the allocation and make the Ethernet header write out of bounds. The race is reproducible on the unpatched kernel. It occurred when vxlan_na_create() generated a neighbour reply while vxlan_changelink() changed the link headroom. KASAN caught a four-byte write two bytes beyond a 704-byte skbuff_small_head allocation. Snapshot the headroom once and use that value for both allocation and reservation.
- Products
- Kernel
- Affected versions
- Not specified
- Fixed versions
- 5.10.273, 5.15.224, 6.1.191, 6.12.112, 6.18.55, 6.6.158, 7.2.9
- CVEs
- CVE-2026-98568
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 06:33 UTC · Revision 1
Source evidence
vxlan: use one headroom snapshot for neighbour replies
core-osv · Original sourcePublished 18 Oct 2026, 15:18 UTC
In the Linux kernel, the following vulnerability has been resolved: vxlan: use one headroom snapshot for neighbour replies vxlan_na_create() samples LL_RESERVED_SPACE() to size the reply skb and then samples it again to reserve headroom. A concurrent vxlan_changelink() can update needed_headroom between the two reads, creating a TOCTOU race. The second value can exceed the allocation and make the Ethernet header write out of bounds. The race is reproducible on the unpatched kernel. It occurred when vxlan_na_create() generated a neighbour reply while vxlan_changelink() changed the link headroom. KASAN caught a four-byte write two bytes beyond a 704-byte skbuff_small_head allocation. Snapshot the headroom once and use that value for both allocation and reservation.
osv:CVE-2026-98568
Kernel
Fixed versions: 5.10.273, 5.15.224, 6.1.191, 6.6.158, 6.12.112, 6.18.55, 7.2.9
Complete source record
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