CVE-2026-63994 PUBLISHED

tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()

Assigner: Linux
Reserved: 19.07.2026 Published: 19.07.2026 Updated: 20.07.2026

In the Linux kernel, the following vulnerability has been resolved:

tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmpv6

Sashiko found that iptunnel_pmtud_build_icmp() and iptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr() before an skb_cow() call which can reallocate skb->head.

Fix this possible UAF by initializing the local variables after the skb_cow() call.

Remove skb_reset_network_header() calls which were not needed.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 9.8

Product Status

Vendor Linux
Product Linux
Versions Default: unaffected
  • affected from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f to 95b6d772bfe788331d9742d73eaa12e113b2adc4 (excl.)
  • affected from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f to 7254aef4d1a7e18e887af9010e2f2dc34806789b (excl.)
  • affected from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f to bf8b3f34c37c162357138e7c0942723b8b94fed1 (excl.)
  • affected from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f to 76cd9398a0470257ab765bdf5f358a2af2e17934 (excl.)
  • affected from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f to 50750d86a2e5266aba0c295483b3397843198b11 (excl.)
  • affected from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f to 6dff77899b9e9fe5d854abda3a98ad04e7229ef7 (excl.)
  • affected from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f to f3f204541f280a6ecb04503a0d6794d93990ca43 (excl.)
  • affected from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f to b4bc94353050b1fa7b702bd4c6600710dd926cff (excl.)
Vendor Linux
Product Linux
Versions Default: affected
  • Version 5.9 is affected
  • unaffected from 0 to 5.9 (excl.)
  • unaffected from 5.10.259 to 5.10.* (incl.)
  • unaffected from 5.15.210 to 5.15.* (incl.)
  • unaffected from 6.1.176 to 6.1.* (incl.)
  • unaffected from 6.6.143 to 6.6.* (incl.)
  • unaffected from 6.12.93 to 6.12.* (incl.)
  • unaffected from 6.18.35 to 6.18.* (incl.)
  • unaffected from 7.0.12 to 7.0.* (incl.)
  • unaffected from 7.1 to * (incl.)

References