{"id":"CVE-2026-89789","state":"PUBLISHED","title":"gtp: add synchronize_net() in gtp_newlink() error path to prevent use-after-free","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ngtp: add synchronize_net() in gtp_newlink() error path to prevent use-after-free\n\ngtp_newlink()'s error path frees tid_hash and addr_hash without\nwaiting for an RCU grace period after clearing sk_user_data. A\nconcurrent gtp_encap_recv() in softirq may still hold the gtp_dev\npointer obtained via rcu_dereference_sk_user_data() and access the\nfreed memory.\n\n  BUG: KASAN: slab-use-after-free in gtp0_pdp_find+0x1f6/0x200 (gtp.c:152)\n  Call Trace:\n   <IRQ>\n   gtp0_pdp_find+0x1f6/0x200\n   gtp_encap_recv+0x527/0x24b0\n   udp_queue_rcv_one_skb+0x75f/0xc10\n\nAdd synchronize_net() before the kfree calls in out_hashtable, which\ncovers all error paths from both gtp_encap_enable() and\ngtp_create_sockets().","publishedAt":"2026-09-16T08:48:25.689Z","updatedAt":"2026-10-19T08:52:43.083Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"fcafb2b1430824bae4258c01a439ec97ca0c6973","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"3ca3da5c305caa873ddb81e8c6b118143f6dd3d1","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"6f815c2fb6ab20385f81c353cdad0ea3b88132af","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"e3b9aa0773abd5d4ed90be41ce5306c146d5b09e","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"fd8396cfecbd904468c71362f08aaa25f96d5337","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"7677eb2cbf2cc7446de474c01a6b06277c0051e5","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"8d85498016a5bb56339734a14c276209fa65bafc","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"d989e22ae9802c52c56ad4284d0caf26696cf6ae","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/gtp.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.7","versionType":"semver"},{"version":"5.10.270","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.221","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.110","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/gtp.c"]}],"references":["https://git.kernel.org/stable/c/fcafb2b1430824bae4258c01a439ec97ca0c6973","https://git.kernel.org/stable/c/3ca3da5c305caa873ddb81e8c6b118143f6dd3d1","https://git.kernel.org/stable/c/6f815c2fb6ab20385f81c353cdad0ea3b88132af","https://git.kernel.org/stable/c/e3b9aa0773abd5d4ed90be41ce5306c146d5b09e","https://git.kernel.org/stable/c/fd8396cfecbd904468c71362f08aaa25f96d5337","https://git.kernel.org/stable/c/7677eb2cbf2cc7446de474c01a6b06277c0051e5","https://git.kernel.org/stable/c/8d85498016a5bb56339734a14c276209fa65bafc","https://git.kernel.org/stable/c/d989e22ae9802c52c56ad4284d0caf26696cf6ae"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:26.108Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/89xxx/CVE-2026-89789.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89789","state":"PUBLISHED","datePublished":"2026-09-16T08:48:25.689Z","dateUpdated":"2026-10-19T08:52:43.083Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.766Z"},"containers":{"cna":{"title":"gtp: add synchronize_net() in gtp_newlink() error path to prevent use-after-free","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ngtp: add synchronize_net() in gtp_newlink() error path to prevent use-after-free\n\ngtp_newlink()'s error path frees tid_hash and addr_hash without\nwaiting for an RCU grace period after clearing sk_user_data. A\nconcurrent gtp_encap_recv() in softirq may still hold the gtp_dev\npointer obtained via rcu_dereference_sk_user_data() and access the\nfreed memory.\n\n  BUG: KASAN: slab-use-after-free in gtp0_pdp_find+0x1f6/0x200 (gtp.c:152)\n  Call Trace:\n   <IRQ>\n   gtp0_pdp_find+0x1f6/0x200\n   gtp_encap_recv+0x527/0x24b0\n   udp_queue_rcv_one_skb+0x75f/0xc10\n\nAdd synchronize_net() before the kfree calls in out_hashtable, which\ncovers all error paths from both gtp_encap_enable() and\ngtp_create_sockets()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"fcafb2b1430824bae4258c01a439ec97ca0c6973","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"3ca3da5c305caa873ddb81e8c6b118143f6dd3d1","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"6f815c2fb6ab20385f81c353cdad0ea3b88132af","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"e3b9aa0773abd5d4ed90be41ce5306c146d5b09e","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"fd8396cfecbd904468c71362f08aaa25f96d5337","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"7677eb2cbf2cc7446de474c01a6b06277c0051e5","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"8d85498016a5bb56339734a14c276209fa65bafc","versionType":"git"},{"version":"459aa660eb1d8ce67080da1983bb81d716aa5a69","status":"affected","lessThan":"d989e22ae9802c52c56ad4284d0caf26696cf6ae","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/gtp.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.7","versionType":"semver"},{"version":"5.10.270","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.221","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.110","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/gtp.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/fcafb2b1430824bae4258c01a439ec97ca0c6973"},{"url":"https://git.kernel.org/stable/c/3ca3da5c305caa873ddb81e8c6b118143f6dd3d1"},{"url":"https://git.kernel.org/stable/c/6f815c2fb6ab20385f81c353cdad0ea3b88132af"},{"url":"https://git.kernel.org/stable/c/e3b9aa0773abd5d4ed90be41ce5306c146d5b09e"},{"url":"https://git.kernel.org/stable/c/fd8396cfecbd904468c71362f08aaa25f96d5337"},{"url":"https://git.kernel.org/stable/c/7677eb2cbf2cc7446de474c01a6b06277c0051e5"},{"url":"https://git.kernel.org/stable/c/8d85498016a5bb56339734a14c276209fa65bafc"},{"url":"https://git.kernel.org/stable/c/d989e22ae9802c52c56ad4284d0caf26696cf6ae"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The UAF is triggered from gtp_newlink()'s RTM_NEWLINK error path (ip link add type gtp), a local rtnetlink configuration interface. Concurrent gtp_encap_recv() in softirq only uses already-freed tid_hash/addr_hash; a remote GTP-U peer cannot cause the free.\nAC:L - The attacker controls both sides of the RCU race: one thread issues RTM_NEWLINK that fails after setup_udp_tunnel_sock() (invalid second FD, IPv4/IPv6 family mismatch, or register_netdevice failure) while another floods UDP datagrams at the encap socket so gtp_encap_recv() still holds the gtp_dev pointer across the kfree.\nPR:L - Creating a GTP device requires CAP_NET_ADMIN in the target netns via rtnl_link_get_net_capable()/netlink_ns_capable(). Unprivileged users obtain this through user+network namespaces (unshare -Urn); gtp_link_ops has no extra init-namespace check and MODULE_ALIAS_RTNL_LINK(\"gtp\") permits module autoload.\nUI:N - The attacker opens its own UDP sockets, sends packets to them, and issues the failing RTM_NEWLINK from its own process. No separate victim action such as mounting a filesystem or opening a file is required.\nS:U - Impact is a host-kernel slab use-after-free in drivers/net/gtp.c, i.e. standard local privilege escalation within the same kernel security authority, not a KVM/Xen guest-to-host escape or IOMMU/DMA boundary bypass.\nC:H - gtp0_pdp_find()/gtp1_pdp_find() walk the attacker-sized freed tid_hash hlist under RCU. Heap spraying that slab yields a fake pdp_ctx and an arbitrary kernel read primitive, so Confidentiality is High per UAF guidance.\nI:H - A sprayed fake pdp_ctx is passed to gtp_rx(), which writes device stats, assigns skb->dev, and calls __netif_rx(); combined with UAF heap reuse this is an arbitrary write and control-flow hijack primitive, so Integrity is High.\nA:H - KASAN reports slab-use-after-free in gtp0_pdp_find from gtp_encap_recv in softirq (udp_queue_rcv_one_skb). The UAF causes a kernel oops or panic even when not fully exploited, so Availability is High."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T08:52:43.083Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"5.10.270"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"5.15.221"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"6.1.188"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"6.6.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"6.12.110"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"6.18.52"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"7.2.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}