CVE-2026-74582 packet: use consistent hard_header_len in non-ring send paths

High 7.8 Published 21 Aug 2026 Updated 16 Oct 2026

A race condition in the Linux kernel packet socket implementation allows out-of-bounds writes, potentially leading to code execution or privilege escalation.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-74582?

CVE-2026-74582 is a high-severity vulnerability in Linux, published on 21 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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.

Which versions are affected by CVE-2026-74582?

Linux distribution packages (40)

`bpftool` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`bpftool-debuginfo` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-abi-stablelists` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-core` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug-core` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug-debuginfo` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug-devel` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug-modules` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug-modules-extra` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debuginfo` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debuginfo-common-ppc64le` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debuginfo-common-x86_64` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-devel` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-doc` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-modules` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-modules-extra` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-tools` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-tools-debuginfo` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-tools-libs` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`perf` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`perf-debuginfo` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`python3-perf` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`python3-perf-debuginfo` Red Hat:rhel_e4s:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`bpftool` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`bpftool-debuginfo` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-abi-stablelists` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-core` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug-core` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug-debuginfo` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug-devel` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug-modules` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debug-modules-extra` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debuginfo` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-debuginfo-common-x86_64` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-devel` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`
`kernel-doc` Red Hat:rhel_tus:8.8::baseos	All versions	`0:4.18.0-477.165.1.el8_8`

How do I fix CVE-2026-74582?

Apply the vendor's patch.

Is CVE-2026-74582 being exploited?

There is no known exploitation of CVE-2026-74582 in the wild and no public exploit code.

Sources

Also known as AZL-96995, BELL-CVE-2026-74582, DEBIAN-CVE-2026-74582, GHSA-6g47-hqw2-hv2r, RHSA-2026:63537, UBUNTU-CVE-2026-74582.