CVE-2026-74582: Linux

High severity, CVSS 7.8. EPSS: 0.1% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: packet: use consistent hard_header_len in non-ring send paths packet_snd() reads dev->hard_header_len multiple times while allocating and constructing an skb. Device reconfiguration can change this value concurrently, for example through bonding device type changes. For SOCK_RAW, packet_snd() can save a larger value in reserve and later allocate headroom using a smaller value. Moving skb->data back by reserve then places it before skb->head, and the following copy from userspace can attempt an out-of-bounds write. packet_sendmsg_spkt() has the same issue because it calculates its reservation and header offset from separate reads before dropping the RCU read lock to allocate the skb. Add LL_RESERVED_SPACE_EX() for callers that already saved a header length. Read hard_header_len once in packet_snd() and use it for allocation and construction. In packet_sendmsg_spkt(), preserve the allocation-time value through the device lookup retry. The separate SOCK_DGRAM consistency problem between hard_header_len and header_ops->create is not addressed here.

Affected products

• Linux Linux: from 4.4.133, before 4.5 (fixed in 4.5); from 4.9.103, before 4.10 (fixed in 4.10); from 4.14.44, before 4.15 (fixed in 4.15); from 4.16.12, before 4.17 (fixed in 4.17); from 4.17, before 5.10.267 (fixed in 5.10.267); from 5.11, before 5.15.218 (fixed in 5.15.218); …

Published 2026-08-21. Last modified 2026-08-27.