Critical severity · published Jul 19, 2026
CVE-2026-63994
tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()
9.8
CVSS
0.5%
EPSS
No
On KEV
Description
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 44% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KE
Kernel · Linux
5.9 before 5.10.259; 5.11 before 5.15.210; 5.16 before 6.1.176; 6.2 before 6.6.143; 6.7 before 6.12.93; 6.13 before 6.18.35; +6 more · source: NVD
LI
Linux · Linux
4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 95b6d772bfe788331d9742d73eaa12e113b2adc4; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 7254aef4d1a7e18e887af9010e2f2dc34806789b; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before bf8b3f34c37c162357138e7c0942723b8b94fed1; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 76cd9398a0470257ab765bdf5f358a2af2e17934; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 50750d86a2e5266aba0c295483b3397843198b11; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 6dff77899b9e9fe5d854abda3a98ad04e7229ef7; +3 more · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-63994
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-63994
Patch
https://git.kernel.org/stable/c/50750d86a2e5266aba0c295483b3397843198b11
Patch
https://git.kernel.org/stable/c/6dff77899b9e9fe5d854abda3a98ad04e7229ef7
Patch
https://git.kernel.org/stable/c/7254aef4d1a7e18e887af9010e2f2dc34806789b
Patch
https://git.kernel.org/stable/c/76cd9398a0470257ab765bdf5f358a2af2e17934
Patch
https://git.kernel.org/stable/c/95b6d772bfe788331d9742d73eaa12e113b2adc4
Patch
https://git.kernel.org/stable/c/b4bc94353050b1fa7b702bd4c6600710dd926cff
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