Answer in brief
CVE-2026-43037 records a Critical severity (CVSS 9.8) vulnerability in ip6_tunnel: clear skb2->cb[] in ip4ip6_err(). 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:7.0:rc1:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=c4d3efafcc933fd2ffd169d7dc4f980393a13796 <ea9f65b27c8404e164848ebff1443310fd187629 || >=c4d3efafcc933fd2ffd169d7dc4f980393a13796 <d6621f60192fe10c047a4487be42a6f4c150707f || >=c4d3efafcc933fd2ffd169d7dc4f980393a13796 <2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5 || >=c4d3efafcc933fd2ffd169d7dc4f980393a13796 <a0c4ce9900a108eaf55d0f3b399cb55999647d39 || >=c4d3efafcc933fd2ffd169d7dc4f980393a13796 <1063515ce15ff31065c4e7f8265f4c2fd3c54876 || >=c4d3efafcc933fd2ffd169d7dc4f980393a13796 <590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3 || >=c4d3efafcc933fd2ffd169d7dc4f980393a13796 <4a622658f384b03560834cbe8ffcfe69a278f7c8 || >=c4d3efafcc933fd2ffd169d7dc4f980393a13796 <2edfa31769a4add828a7e604b21cb82aaaa05925 | ea9f65b27c8404e164848ebff1443310fd187629, d6621f60192fe10c047a4487be42a6f4c150707f, 2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5, a0c4ce9900a108eaf55d0f3b399cb55999647d39, 1063515ce15ff31065c4e7f8265f4c2fd3c54876, 590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3, 4a622658f384b03560834cbe8ffcfe69a278f7c8, 2edfa31769a4add828a7e604b21cb82aaaa05925 |
| Linux/Linuxgeneric | 2.6.22 | Not reported |
Published upstream
May 1, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 1, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 1, 2026
In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: clear skb2->cb[] in ip4ip6_err() Oskar Kjos reported the following problem. ip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written by the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes IPCB(skb2) to __ip_options_echo(), which interprets that cb[] region as struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff at offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr value. __ip_options_echo() then reads optlen from attacker-controlled packet data at sptr[rr+1] and copies that many bytes into dopt->__data, a fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE). To fix this we clear skb2->cb[], as suggested by Oskar Kjos. Also add minimal IPv4 header validation (version == 4, ihl >= 5).
Quoted source text, attributed separately from HOL analysis.