CVE-2026-43037 (GCVE-0-2026-43037)

Vulnerability from cvelistv5 – Published: 2026-05-01 14:15 – Updated: 2026-05-11 22:16
VLAI
Title
ip6_tunnel: clear skb2->cb[] in ip4ip6_err()
Summary
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).
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < ea9f65b27c8404e164848ebff1443310fd187629 (git)
Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < d6621f60192fe10c047a4487be42a6f4c150707f (git)
Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < 2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5 (git)
Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < a0c4ce9900a108eaf55d0f3b399cb55999647d39 (git)
Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < 1063515ce15ff31065c4e7f8265f4c2fd3c54876 (git)
Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < 590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3 (git)
Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < 4a622658f384b03560834cbe8ffcfe69a278f7c8 (git)
Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < 2edfa31769a4add828a7e604b21cb82aaaa05925 (git)
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Linux Linux Affected: 2.6.22
Unaffected: 0 , < 2.6.22 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.168 , ≤ 6.1.* (semver)
Unaffected: 6.6.134 , ≤ 6.6.* (semver)
Unaffected: 6.12.81 , ≤ 6.12.* (semver)
Unaffected: 6.18.22 , ≤ 6.18.* (semver)
Unaffected: 6.19.12 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.