Critical 9.8Published Jul 19, 2026

CVE-2026-63994tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()

Updated under an hour ago (Oct 26, 2026, 6:40 PM ET)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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.

CVSS: 9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-416
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 19, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 95b6d772bfe788331d9742d73eaa12e113b2adc4; from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 7254aef4d1a7e18e887af9010e2f2dc34806789b; from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before bf8b3f34c37c162357138e7c0942723b8b94fed1; from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 76cd9398a0470257ab765bdf5f358a2af2e17934; from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 50750d86a2e5266aba0c295483b3397843198b11; from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 6dff77899b9e9fe5d854abda3a98ad04e7229ef7; from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before f3f204541f280a6ecb04503a0d6794d93990ca43; from 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before b4bc94353050b1fa7b702bd4c6600710dd926cff	CNA record
linux linux_kernel linux:linux_kernel	from 5.9 before 5.10.259; from 5.11 before 5.15.210; from 5.16 before 6.1.176; from 6.2 before 6.6.143; from 6.7 before 6.12.93; from 6.13 before 6.18.35; from 6.19 before 7.0.12; 7.1; and 4 more ranges	NVD

References

References

https://git.kernel.org/stable/c/95b6d772bfe788331d9742d73eaa12e113b2adc4	patch
https://git.kernel.org/stable/c/7254aef4d1a7e18e887af9010e2f2dc34806789b	patch
https://git.kernel.org/stable/c/bf8b3f34c37c162357138e7c0942723b8b94fed1	patch
https://git.kernel.org/stable/c/76cd9398a0470257ab765bdf5f358a2af2e17934	patch
https://git.kernel.org/stable/c/50750d86a2e5266aba0c295483b3397843198b11	patch
https://git.kernel.org/stable/c/6dff77899b9e9fe5d854abda3a98ad04e7229ef7	patch
https://git.kernel.org/stable/c/f3f204541f280a6ecb04503a0d6794d93990ca43	patch
https://git.kernel.org/stable/c/b4bc94353050b1fa7b702bd4c6600710dd926cff	patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.