{"api_version":"1","generated_at":"2026-08-13T02:01:01+00:00","cve":"CVE-2026-68398","urls":{"html":"https://cve.report/CVE-2026-68398","api":"https://cve.report/api/cve/CVE-2026-68398.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-68398","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-68398"},"summary":{"title":"ppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF\n\npppol2tp_recv() runs in the L2TP UDP-encap softirq RX path:\n\n l2tp_udp_encap_recv() -> l2tp_recv_common() -> pppol2tp_recv()\n   -> ppp_input(&po->chan)\n\nIt runs under rcu_read_lock() holding only an l2tp_session reference and\ntakes NO reference on the internal PPP channel (struct channel,\nchan->ppp) that ppp_input() dereferences.\n\nThe pppox socket is SOCK_RCU_FREE, so 'po' and the embedded ppp_channel\nare RCU-safe.  But the internal struct channel is a separate allocation\nthat ppp_release_channel() frees with a plain kfree():\n\n close(data socket) -> pppol2tp_release() -> pppox_unbind_sock()\n   -> ppp_unregister_channel() -> ppp_release_channel() -> kfree(pch)\n\nFor a channel that is bound (PPPIOCGCHAN) but not attached to a ppp unit\n(no PPPIOCCONNECT, pch->ppp == NULL) and not bridged, teardown skips\nboth ppp_disconnect_channel()'s synchronize_net() and\nppp_unbridge_channels()'s synchronize_rcu(), so the kfree() has no grace\nperiod.  rcu_read_lock() in pppol2tp_recv() does not protect against a\nplain kfree(), so an in-flight ppp_input() on one CPU can dereference\nthe channel just freed by close() on another CPU.\n\nThe bug is reachable by an unprivileged user.\n\nDefer the channel free to an RCU callback via call_rcu() so the grace\nperiod fences any in-flight ppp_input(). The disconnect and unbridge\nteardown paths already fence with synchronize_net()/synchronize_rcu();\ncall_rcu() does the same here without stalling the close() path.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-08-10 13:20:33","updated_at":"2026-08-10 13:20:33"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/4bb84e964ff0fe0a171c965362de72f9820dbce9","name":"https://git.kernel.org/stable/c/4bb84e964ff0fe0a171c965362de72f9820dbce9","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ec4215683e47424c9c4762fd3c60f552a3119142","name":"https://git.kernel.org/stable/c/ec4215683e47424c9c4762fd3c60f552a3119142","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/06213c85d8c0994f786c093b8b2a517987943ca6","name":"https://git.kernel.org/stable/c/06213c85d8c0994f786c093b8b2a517987943ca6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/c9574b8a8edeb4edd3ac6472c27ef7184bdb2baa","name":"https://git.kernel.org/stable/c/c9574b8a8edeb4edd3ac6472c27ef7184bdb2baa","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/3ab32218d7182705dae5c86f13925f458072da2c","name":"https://git.kernel.org/stable/c/3ab32218d7182705dae5c86f13925f458072da2c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-68398","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68398","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 4bb84e964ff0fe0a171c965362de72f9820dbce9 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 3ab32218d7182705dae5c86f13925f458072da2c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 c9574b8a8edeb4edd3ac6472c27ef7184bdb2baa git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 06213c85d8c0994f786c093b8b2a517987943ca6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4.4.225 4.5 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4.9.225 4.10 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4.14.182 4.15 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4.15","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 4.15 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.148 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.101 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.42 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1.6 7.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2-rc4 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["drivers/net/ppp/ppp_generic.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"4bb84e964ff0fe0a171c965362de72f9820dbce9","status":"affected","version":"ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741","versionType":"git"},{"lessThan":"3ab32218d7182705dae5c86f13925f458072da2c","status":"affected","version":"ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741","versionType":"git"},{"lessThan":"c9574b8a8edeb4edd3ac6472c27ef7184bdb2baa","status":"affected","version":"ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741","versionType":"git"},{"lessThan":"06213c85d8c0994f786c093b8b2a517987943ca6","status":"affected","version":"ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741","versionType":"git"},{"lessThan":"ec4215683e47424c9c4762fd3c60f552a3119142","status":"affected","version":"ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741","versionType":"git"},{"status":"affected","version":"d36e5ba7bbed5d7bd26e8609ffed503c2def401b","versionType":"git"},{"status":"affected","version":"9bcc0508576b2d50efd958f2ea1c5906749c2c89","versionType":"git"},{"status":"affected","version":"c2984681fe15cfb803a9132aaaf1140ab20a72c1","versionType":"git"},{"status":"affected","version":"5803ecd7f6ac6f747582e775caa62ac9d0489261","versionType":"git"},{"status":"affected","version":"26f8819ddd10141ebe7bbce700fbab36bfa5f478","versionType":"git"},{"lessThan":"3.3","status":"affected","version":"3.2.99","versionType":"semver"},{"lessThan":"3.17","status":"affected","version":"3.16.54","versionType":"semver"},{"lessThan":"4.5","status":"affected","version":"4.4.225","versionType":"semver"},{"lessThan":"4.10","status":"affected","version":"4.9.225","versionType":"semver"},{"lessThan":"4.15","status":"affected","version":"4.14.182","versionType":"semver"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["drivers/net/ppp/ppp_generic.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"4.15"},{"lessThan":"4.15","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.148","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.101","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.42","versionType":"semver"},{"lessThanOrEqual":"7.1.*","status":"unaffected","version":"7.1.6","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.2-rc4","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.148","versionStartIncluding":"4.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.101","versionStartIncluding":"4.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.42","versionStartIncluding":"4.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1.6","versionStartIncluding":"4.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2-rc4","versionStartIncluding":"4.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.2.99","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16.54","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.4.225","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9.225","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.14.182","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF\n\npppol2tp_recv() runs in the L2TP UDP-encap softirq RX path:\n\n l2tp_udp_encap_recv() -> l2tp_recv_common() -> pppol2tp_recv()\n   -> ppp_input(&po->chan)\n\nIt runs under rcu_read_lock() holding only an l2tp_session reference and\ntakes NO reference on the internal PPP channel (struct channel,\nchan->ppp) that ppp_input() dereferences.\n\nThe pppox socket is SOCK_RCU_FREE, so 'po' and the embedded ppp_channel\nare RCU-safe.  But the internal struct channel is a separate allocation\nthat ppp_release_channel() frees with a plain kfree():\n\n close(data socket) -> pppol2tp_release() -> pppox_unbind_sock()\n   -> ppp_unregister_channel() -> ppp_release_channel() -> kfree(pch)\n\nFor a channel that is bound (PPPIOCGCHAN) but not attached to a ppp unit\n(no PPPIOCCONNECT, pch->ppp == NULL) and not bridged, teardown skips\nboth ppp_disconnect_channel()'s synchronize_net() and\nppp_unbridge_channels()'s synchronize_rcu(), so the kfree() has no grace\nperiod.  rcu_read_lock() in pppol2tp_recv() does not protect against a\nplain kfree(), so an in-flight ppp_input() on one CPU can dereference\nthe channel just freed by close() on another CPU.\n\nThe bug is reachable by an unprivileged user.\n\nDefer the channel free to an RCU callback via call_rcu() so the grace\nperiod fences any in-flight ppp_input(). The disconnect and unbridge\nteardown paths already fence with synchronize_net()/synchronize_rcu();\ncall_rcu() does the same here without stalling the close() path."}],"providerMetadata":{"dateUpdated":"2026-08-10T12:04:17.771Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/4bb84e964ff0fe0a171c965362de72f9820dbce9"},{"url":"https://git.kernel.org/stable/c/3ab32218d7182705dae5c86f13925f458072da2c"},{"url":"https://git.kernel.org/stable/c/c9574b8a8edeb4edd3ac6472c27ef7184bdb2baa"},{"url":"https://git.kernel.org/stable/c/06213c85d8c0994f786c093b8b2a517987943ca6"},{"url":"https://git.kernel.org/stable/c/ec4215683e47424c9c4762fd3c60f552a3119142"}],"title":"ppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-68398","datePublished":"2026-08-10T12:04:17.771Z","dateReserved":"2026-07-30T09:28:09.389Z","dateUpdated":"2026-08-10T12:04:17.771Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-10 13:20:33","lastModifiedDate":"2026-08-10 13:20:33","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"68398","Ordinal":"1","Title":"ppp: defer channel free to an RCU grace period to fix pppol2tp R","CVE":"CVE-2026-68398","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"68398","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF\n\npppol2tp_recv() runs in the L2TP UDP-encap softirq RX path:\n\n l2tp_udp_encap_recv() -> l2tp_recv_common() -> pppol2tp_recv()\n   -> ppp_input(&po->chan)\n\nIt runs under rcu_read_lock() holding only an l2tp_session reference and\ntakes NO reference on the internal PPP channel (struct channel,\nchan->ppp) that ppp_input() dereferences.\n\nThe pppox socket is SOCK_RCU_FREE, so 'po' and the embedded ppp_channel\nare RCU-safe.  But the internal struct channel is a separate allocation\nthat ppp_release_channel() frees with a plain kfree():\n\n close(data socket) -> pppol2tp_release() -> pppox_unbind_sock()\n   -> ppp_unregister_channel() -> ppp_release_channel() -> kfree(pch)\n\nFor a channel that is bound (PPPIOCGCHAN) but not attached to a ppp unit\n(no PPPIOCCONNECT, pch->ppp == NULL) and not bridged, teardown skips\nboth ppp_disconnect_channel()'s synchronize_net() and\nppp_unbridge_channels()'s synchronize_rcu(), so the kfree() has no grace\nperiod.  rcu_read_lock() in pppol2tp_recv() does not protect against a\nplain kfree(), so an in-flight ppp_input() on one CPU can dereference\nthe channel just freed by close() on another CPU.\n\nThe bug is reachable by an unprivileged user.\n\nDefer the channel free to an RCU callback via call_rcu() so the grace\nperiod fences any in-flight ppp_input(). The disconnect and unbridge\nteardown paths already fence with synchronize_net()/synchronize_rcu();\ncall_rcu() does the same here without stalling the close() path.","Type":"Description","Title":"ppp: defer channel free to an RCU grace period to fix pppol2tp R"}]}}}