{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-63921 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-63921 is a high-severity missing authorization vulnerability in Linux kernel, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-63921 and fix it if it is affected.\n\nWhat it is: CVE-2026-63921 is a high-severity missing authorization vulnerability in Linux kernel, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-63921 in the wild and no public exploit code.\n\nAffected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-63921/ (Markdown: https://insights.sbomify.com/CVE-2026-63921/index.md)","id":"CVE-2026-63921","markdown":"https://insights.sbomify.com/CVE-2026-63921/index.md","name":"CVE-2026-63921","record":{"aliases":["BELL-CVE-2026-63921","DEBIAN-CVE-2026-63921","GHSA-c82w-wxq7-hwv4","ROOT-OS-UBUNTU-2204-CVE-2026-63921","UBUNTU-CVE-2026-63921"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["privilege_escalation","data_read"],"network_reachable":"adjacent_or_local","non_default_config":false,"product_category":"Linux kernel","requires_auth":"low_privilege","summary":"An attacker in an unprivileged user namespace can hijack IPv6 tunnel traffic across network namespaces, leading to privilege escalation and data interception.","user_interaction":"not_required","vuln_class":"missing_authorization"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[{"product":"linux_kernel","vendor":"linux"}],"cvss":{"score":8.8,"severity":"high","source":"cna","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","version":"3.1"},"cwes":[{"id":"CWE-862","name":"Missing Authorization"}],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nip6: vti: Use ip6_tnl.net in vti6_siocdevprivate().\n\nAfter patch 1/2 in this series, vti6_update() unlinks and relinks\nthe tunnel through t-\u003enet. vti6_siocdevprivate() still uses\ndev_net(dev) for the collision lookup. For a tunnel moved through\nIFLA_NET_NS_FD, dev_net(dev) is the new netns, not t-\u003enet.\n\nSIOCCHGTUNNEL on a migrated tunnel then runs:\n\n  net = dev_net(dev)                    /* migrated netns */\n  t   = vti6_locate(net, \u0026p1, false)    /* misses target in t-\u003enet */\n  ...\n  t   = netdev_priv(dev)\n  vti6_update(t, \u0026p1, false)            /* mutates t-\u003enet's hash */\n\nA caller in the migrated netns picks params that match a tunnel\nin the creation netns. The lookup in dev_net(dev) finds nothing.\nvti6_update() prepends the migrated tunnel at the head of the\ncreation netns hash bucket for those params. Later lookups in\nthe creation netns resolve to the migrated device. xfrm receive\ndelivers the matched packets through a device the caller controls.\n\nReachable from an unprivileged user namespace (unshare --user\n--map-root-user --net). Cross tenant scope on container hosts.\n\nSwitch the SIOCCHGTUNNEL path on a non fallback device to use\nt-\u003enet for the lookup. The lookup now matches the netns\nvti6_update() operates on.\n\nAlso add ns_capable(self-\u003enet-\u003euser_ns, CAP_NET_ADMIN) before\nthe lookup. The check at the top of the case is against\ndev_net(dev)-\u003euser_ns, which after migration is the attacker's\nnetns. A caller there can pick params absent from self-\u003enet,\nthe lookup returns NULL, t becomes self, and vti6_update()\ninserts the device into the creation netns hash. The new check\nrequires CAP_NET_ADMIN in the creation netns user_ns too.\n\nSIOCADDTUNNEL and SIOCCHGTUNNEL on the fallback device keep\ndev_net(dev), which equals init_net there.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"ip6: vti: Use ip6_tnl.net in vti6_siocdevprivate().","id":"CVE-2026-63921","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"missing_authorization","year":"2026"},"n_packages":0,"n_references":8,"next":{"headline":"ipv6: exthdrs: refresh nh after handling HAO option","id":"CVE-2026-63922"},"packages":[],"prev":{"headline":"ipv6: validate extension header length before copying to cmsg","id":"CVE-2026-63920"},"products":["Linux"],"published":"2026-07-19","related":[{"cvss_score":8.8,"headline":"Linux Kernel Out-of-Bounds Write","id":"CVE-2026-53266","kev_date_added":"2026-09-18","published":"2026-06-25"},{"cvss_score":8.8,"headline":"Linux Kernel Improper Input Validation","id":"CVE-2013-6282","kev_date_added":"2022-09-15","published":"2013-11-19"},{"cvss_score":8.4,"headline":"Linux Kernel Heap-Based Buffer Overflow","id":"CVE-2022-0185","kev_date_added":"2024-08-21","published":"2022-02-11"},{"cvss_score":8.4,"headline":"Linux Kernel Privilege Escalation","id":"CVE-2013-2094","kev_date_added":"2022-09-15","published":"2013-05-14"},{"cvss_score":7.8,"headline":"Linux Kernel Unspecified","id":"CVE-2026-53362","kev_date_added":"2026-08-27","published":"2026-07-04"},{"cvss_score":7.8,"headline":"Linux Kernel Missing Initialization of a Variable","id":"CVE-2026-46300","kev_date_added":"2026-10-28","published":"2026-05-23"},{"cvss_score":7.8,"headline":"Linux Kernel Race Condition","id":"CVE-2025-39964","kev_date_added":"2026-09-18","published":"2025-10-13"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"total"},"state":"PUBLISHED","updated":"2026-10-19","vendors":["Linux"]},"summary":"An attacker in an unprivileged user namespace can hijack IPv6 tunnel traffic across network namespaces, leading to privilege escalation and data interception.","url":"https://insights.sbomify.com/CVE-2026-63921/"}