9.8

CVE-2026-63994: linux Use After Free

CVSS: 9.8v3.1CriticalModified
AliasesUBUNTU-CVE-2026-63994DEBIAN-CVE-2026-63994
Published 19-07-2026Last modified 19-10-2026
Open JSON

Vulnerability summary

CVE-2026-63994 is a critical (CVSS 9.8) Use After Free vulnerability in linux. EPSS estimates a 0.51% chance of exploitation in the next 30 days, higher than 42.5% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.8/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.51%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 162 · Related 159
OPENSUSE-SU-2026:21555-1RHSA-2026:75746RHSA-2026:75747RHSA-2026:76739SUSE-SU-2026:23066-1SUSE-SU-2026:23068-1

Showing 100 of 162. Use Open JSON for the complete list.

Timeline

  1. 19-07-2026
    PublishedVulnerability first disclosed.
  2. 19-10-2026
    Last modifiedVulnerability information updated.

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 metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.51%

Chance of exploitation in the next 30 days

Percentile

43%

Versus all other CVEs

30-day change

0.00 pp

From 0.51% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.51%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Ubuntu155 products
  • linux< 5.15.0-194.204 | < 6.8.0-142.142 | < 7.0.0-28.28
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws< 5.15.0-1116.123 | < 6.8.0-1065.68 | < 7.0.0-1009.9
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 95b6d772bfe788331d9742d73eaa12e113b2adc4 | ≥ 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 7254aef4d1a7e18e887af9010e2f2dc34806789b | ≥ 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < bf8b3f34c37c162357138e7c0942723b8b94fed1 | ≥ 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 76cd9398a0470257ab765bdf5f358a2af2e17934 | ≥ 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 50750d86a2e5266aba0c295483b3397843198b11 | ≥ 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 6dff77899b9e9fe5d854abda3a98ad04e7229ef7 | ≥ 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < f3f204541f280a6ecb04503a0d6794d93990ca43 | ≥ 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < b4bc94353050b1fa7b702bd4c6600710dd926cff | 5.9
  • linux_kernel≥ 5.9, < 5.10.259 | ≥ 5.11, < 5.15.210 | ≥ 5.16, < 6.1.176 | ≥ 6.2, < 6.6.143 | ≥ 6.7, < 6.12.93 | ≥ 6.13, < 6.18.35 | ≥ 6.19, < 7.0.12 | 7.1:rc1 | 7.1:rc2 | 7.1:rc3 | 7.1:rc4 | 7.1:rc5
Debian1 product
  • linux< 6.1.176-1 | < 6.12.94-1 | < 7.0.12-1

3 vendors · 158 products

References

36 links
Show all 36 references