{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63829","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-19T07:54:57.014Z","datePublished":"2026-07-19T12:02:23.191Z","dateUpdated":"2026-08-17T04:51:37.933Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-17T04:51:37.933Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ip_gre: require CAP_NET_ADMIN in the device netns for changelink\n\nA tunnel changelink() operates on at most two netns, dev_net(dev) and\nthe tunnel link netns t->net. They differ once the device is created in\nor moved to a netns other than the one the request runs in. The rtnl\nchangelink path checks CAP_NET_ADMIN only against dev_net(dev), so a\ncaller privileged there but not in t->net can rewrite a tunnel that\nlives in t->net.\n\nAdd rtnl_dev_link_net_capable() next to rtnl_get_net_ns_capable() in\nnet/core/rtnetlink.c. It requires CAP_NET_ADMIN in the link netns and is\nskipped when the link netns is dev_net(dev), where the rtnl path already\nchecked it. The other patches in this series use the same helper.\n\nGate ipgre_changelink() and erspan_changelink() with it, at the top of\nthe op before any attribute is parsed, because the parsers update live\ntunnel fields first. ipgre_netlink_parms() sets t->collect_md before\nip_tunnel_changelink() runs.\n\nCommit 8b484efd5cb4 (\"ip6: vti: Use ip6_tnl.net in\nvti6_siocdevprivate().\") added the same check on the ioctl path. This\nadds it on RTM_NEWLINK."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - Exploitation requires sending RTM_NEWLINK changelink requests over rtnetlink (netlink socket), matching the kernel guidance that tc/netlink configuration paths are Local.\nAC:L - Once a cross-namespace GRE/ERSPAN device is present in the caller's netns, triggering the bug is a single deterministic netlink changelink with no races or attacker-uncontrollable timing.\nPR:L - The rtnl entry path requires CAP_NET_ADMIN in dev_net(dev), which an unprivileged user can obtain inside a user namespace via unshare --user --map-root-user --net without real init-namespace root.\nUI:N - Exploitation is fully programmatic through netlink; no victim user action such as opening a file or mounting a filesystem is required.\nS:C - The changelink mutates tunnel state in t->net while authorization is checked only against dev_net(dev), crossing from the attacker's net/user namespace into another tenant's or the host's network namespace tunnel tables.\nC:H - An attacker can rewrite IFLA_GRE_REMOTE/LOCAL, keys, and related tunnel parameters to redirect GRE/ERSPAN traffic through attacker-controlled endpoints and read tunneled payloads.\nI:H - Unauthorized changelink updates live tunnel fields (including collect_md and encap parameters parsed before the missing check), enabling arbitrary redirection or injection of traffic in the victim link netns.\nA:H - Rewriting tunnel endpoints, keys, or metadata handling can break production GRE/ERSPAN overlays and VPN paths, causing sustained loss of connectivity for dependent services."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/rtnetlink.h","net/core/rtnetlink.c","net/ipv4/ip_gre.c"],"versions":[{"version":"b57708add31494175be741ed3fd24023b50c3423","lessThan":"19275943d8fe903eb7b9aa53e380e41efd042ada","status":"affected","versionType":"git"},{"version":"b57708add31494175be741ed3fd24023b50c3423","lessThan":"866b0f5ae599490bd496fd84581c68ac8b94e6af","status":"affected","versionType":"git"},{"version":"b57708add31494175be741ed3fd24023b50c3423","lessThan":"92b766fc55156e0da2ecd0c2302c971118f8a229","status":"affected","versionType":"git"},{"version":"b57708add31494175be741ed3fd24023b50c3423","lessThan":"e54c05ed3d9c28733fb9e5837219aca3691defa3","status":"affected","versionType":"git"},{"version":"b57708add31494175be741ed3fd24023b50c3423","lessThan":"9831bc9ecb402957810c2045c663fbfe9b09e296","status":"affected","versionType":"git"},{"version":"b57708add31494175be741ed3fd24023b50c3423","lessThan":"1697957eb0971d420dde42862b88eb43506a1105","status":"affected","versionType":"git"},{"version":"b57708add31494175be741ed3fd24023b50c3423","lessThan":"47b5d3d506609b08b2e1f7c14f0b681a1953d572","status":"affected","versionType":"git"},{"version":"b57708add31494175be741ed3fd24023b50c3423","lessThan":"8165f7ff57d9667d2bb477ef6af83ede7fed4ad7","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/rtnetlink.h","net/core/rtnetlink.c","net/ipv4/ip_gre.c"],"versions":[{"version":"3.16","status":"affected"},{"version":"0","lessThan":"3.16","status":"unaffected","versionType":"semver"},{"version":"5.10.261","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.212","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.178","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.145","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.95","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.38","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.3","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16","versionEndExcluding":"5.10.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16","versionEndExcluding":"6.12.95"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16","versionEndExcluding":"6.18.38"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16","versionEndExcluding":"7.1.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16","versionEndExcluding":"7.2"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/19275943d8fe903eb7b9aa53e380e41efd042ada"},{"url":"https://git.kernel.org/stable/c/866b0f5ae599490bd496fd84581c68ac8b94e6af"},{"url":"https://git.kernel.org/stable/c/92b766fc55156e0da2ecd0c2302c971118f8a229"},{"url":"https://git.kernel.org/stable/c/e54c05ed3d9c28733fb9e5837219aca3691defa3"},{"url":"https://git.kernel.org/stable/c/9831bc9ecb402957810c2045c663fbfe9b09e296"},{"url":"https://git.kernel.org/stable/c/1697957eb0971d420dde42862b88eb43506a1105"},{"url":"https://git.kernel.org/stable/c/47b5d3d506609b08b2e1f7c14f0b681a1953d572"},{"url":"https://git.kernel.org/stable/c/8165f7ff57d9667d2bb477ef6af83ede7fed4ad7"}],"title":"net: ip_gre: require CAP_NET_ADMIN in the device netns for changelink","x_generator":{"engine":"bippy-1.2.0"}}}}