Answer in brief
CVE-2026-63994 records a Critical severity (CVSS 9.8) vulnerability in tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6](). The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=4cb47a8644cc9eb8ec81190a50e79e6530d0297f <95b6d772bfe788331d9742d73eaa12e113b2adc4 || >=4cb47a8644cc9eb8ec81190a50e79e6530d0297f <7254aef4d1a7e18e887af9010e2f2dc34806789b || >=4cb47a8644cc9eb8ec81190a50e79e6530d0297f <bf8b3f34c37c162357138e7c0942723b8b94fed1 || >=4cb47a8644cc9eb8ec81190a50e79e6530d0297f <76cd9398a0470257ab765bdf5f358a2af2e17934 || >=4cb47a8644cc9eb8ec81190a50e79e6530d0297f <50750d86a2e5266aba0c295483b3397843198b11 || >=4cb47a8644cc9eb8ec81190a50e79e6530d0297f <6dff77899b9e9fe5d854abda3a98ad04e7229ef7 || >=4cb47a8644cc9eb8ec81190a50e79e6530d0297f <f3f204541f280a6ecb04503a0d6794d93990ca43 || >=4cb47a8644cc9eb8ec81190a50e79e6530d0297f <b4bc94353050b1fa7b702bd4c6600710dd926cff | 95b6d772bfe788331d9742d73eaa12e113b2adc4, 7254aef4d1a7e18e887af9010e2f2dc34806789b, bf8b3f34c37c162357138e7c0942723b8b94fed1, 76cd9398a0470257ab765bdf5f358a2af2e17934, 50750d86a2e5266aba0c295483b3397843198b11, 6dff77899b9e9fe5d854abda3a98ad04e7229ef7, f3f204541f280a6ecb04503a0d6794d93990ca43, b4bc94353050b1fa7b702bd4c6600710dd926cff |
| Linux/Linuxgeneric | 5.9 | Not reported |
Published upstream
Jul 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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.
Quoted source text, attributed separately from HOL analysis.