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CVE-2026-31700

net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd()

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.259, 5.15.210, 6.1.176, 6.6.136, 6.12.84, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

In the Linux kernel, the following vulnerability has been resolved: net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd() In tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points directly into the mmap'd TX ring buffer shared with userspace. The kernel validates the header via __packet_snd_vnet_parse() but then re-reads all fields later in virtio_net_hdr_to_skb(). A concurrent userspace thread can modify the vnet_hdr fields between validation and use, bypassing all safety checks. The non-TPACKET path (packet_snd()) already correctly copies vnet_hdr to a stack-local variable. All other vnet_hdr consumers in the kernel (tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX path is the only caller of virtio_net_hdr_to_skb() that reads directly from user-controlled shared memory. Fix this by copying vnet_hdr from the mmap'd ring buffer to a stack-local variable before validation and use, consistent with the approach used in packet_snd() and all other callers.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 1d036d25e5609ba73fee6a88db01c306b140d512 · fixed in 0f4c9754956b86de158a4af5278c5cf5bda9439e; From 1d036d25e5609ba73fee6a88db01c306b140d512 · fixed in 714aa973da8163925eda7efd49361ccbee21ee46; From 1d036d25e5609ba73fee6a88db01c306b140d512 · fixed in 1490f82353bdabc09265a74e645b07f05cf4188e; From 1d036d25e5609ba73fee6a88db01c306b140d512 · fixed in 74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121; From 1d036d25e5609ba73fee6a88db01c306b140d512 · fixed in 3a1bf9116ea31470b89692585c3910dfe830dcdd; From 1d036d25e5609ba73fee6a88db01c306b140d512 · fixed in 28324a3b62d9ce7f9bdd65a8ce63f382041d1b27; From 1d036d25e5609ba73fee6a88db01c306b140d512 · fixed in 48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b; From 1d036d25e5609ba73fee6a88db01c306b140d512 · fixed in 2c054e17d9d41f1020376806c7f750834ced4dc5

  • Linux Linux

    4.6

  • KernelLinux

    From 4.6.0 · fixed in 5.10.259; From 5.11.0 · fixed in 5.15.210; From 5.16.0 · fixed in 6.1.176; From 6.2.0 · fixed in 6.6.136; From 6.7.0 · fixed in 6.12.84; From 6.13.0 · fixed in 6.18.25; From 6.19.0 · fixed in 7.0.2

References 8

git.kernel.org