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CVE-2026-63994

CRITICALCVSS 9.8/10EPSS 0.52%

Last modified

CVE-2026-63994 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 0.52% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
9.8/10

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

EPSS Probability
0.52%

41.3th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 95b6d772bfe788331d9742d73eaa12e113b2adc4; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 7254aef4d1a7e18e887af9010e2f2dc34806789b; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < bf8b3f34c37c162357138e7c0942723b8b94fed1; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 76cd9398a0470257ab765bdf5f358a2af2e17934; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 50750d86a2e5266aba0c295483b3397843198b11; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 6dff77899b9e9fe5d854abda3a98ad04e7229ef7; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < f3f204541f280a6ecb04503a0d6794d93990ca43; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < b4bc94353050b1fa7b702bd4c6600710dd926cff
LinuxLinux5.9

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-63994?
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.
How severe is CVE-2026-63994?
CVE-2026-63994 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.52% probability of exploitation in the next 30 days.
How do I fix CVE-2026-63994?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST