Critical severity · published Jul 19, 2026
CVE-2026-63992
tunnels: do not assume transport header in iptunnel_pmtud_check_icmp()
9.1
CVSS
0.5%
EPSS
No
On KEV
Description
In the Linux kernel, the following vulnerability has been resolved:
tunnels: do not assume transport header in iptunnel_pmtud_check_icmp()
In some cases, iptunnel_pmtud_check_icmp() can be called while
skb transport header is not set.
This triggers an out-of-bound access, because
(typeof(skb->transport_header))~0U is 65535.
Access the icmp header based on IPv4 network header,
after making sure icmp->type is present in skb linear part.
Note that iptunnel_pmtud_check_icmpv6()) is fine.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
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 5a92cb45e34749865d03daf8d3500f77b5f6644c; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before c7b7ec3e69e673c0d6b57f74d21da50c485c598e; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 7f4f7efe7f30edd29c4988de01728bf2398217e4; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before a096b6e34f602950af9a2b0856cd93a5f4c276d7; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f before 43368636c663cff6e59dde93cf4b8e43ac28eb93; +3 more · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-63992
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-63992
Patch
https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93
Patch
https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d
Patch
https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c
Patch
https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4
Patch
https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7
Patch
https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e
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