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

Summary

In the Linux kernel, the following vulnerability has been resolved: tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]() 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.

Timeline

1. Jul 19, 2026, 2:56 PM UTCCVE published
2. Oct 16, 2026, 3:34 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: total

3. Oct 19, 2026, 8:18 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in 95b6d772bfe788331d9742d73eaa12e113b2adc4; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in 7254aef4d1a7e18e887af9010e2f2dc34806789b; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in bf8b3f34c37c162357138e7c0942723b8b94fed1; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in 76cd9398a0470257ab765bdf5f358a2af2e17934; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in 50750d86a2e5266aba0c295483b3397843198b11; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in 6dff77899b9e9fe5d854abda3a98ad04e7229ef7; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in f3f204541f280a6ecb04503a0d6794d93990ca43; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in b4bc94353050b1fa7b702bd4c6600710dd926cff

• Linux Linux

  5.9

• KernelLinux

  From 5.9.0 · 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 6.6.143; From 6.7.0 · fixed in 6.12.93; From 6.13.0 · fixed in 6.18.35; From 6.19.0 · fixed in 7.0.12

References 8