{"id":"CVE-2026-74735","state":"PUBLISHED","title":"l2tp: fix tunnel and session refcount leak on seq_file release","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nl2tp: fix tunnel and session refcount leak on seq_file release\n\nIn pppol2tp_proc_open() and l2tp_dfs_seq_open(), iteration state\n(pd->tunnel and pd->session) is kept in seq_file private data to allow\niteration across multiple read() system calls.\n\nHowever, if userspace closes /proc/net/pppol2tp or /sys/kernel/debug/l2tp/tunnels\nbefore reading to end-of-file (EOF), any tunnel or session reference stored in\npd->tunnel / pd->session is left un-dropped when seq_file private data is freed.\n\nFix this by dropping any remaining pd->tunnel and pd->session references in\npppol2tp_proc_release() and l2tp_dfs_seq_release() when closing the file.","publishedAt":"2026-08-26T14:36:49.352Z","updatedAt":"2026-10-30T12:30:27.082Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"c38b723858a51d6ca4e56470b9f1087f23276772","versionType":"git"},{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"bd897e414451fb34dfdf08b31899180e5ab7149b","versionType":"git"},{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"bdf83613781956cc39798ed08321f74ab0467f4d","versionType":"git"},{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"8c4fde01bcf91f22b9c7ded8c3e14addd7ddd500","versionType":"git"},{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"ebe2774e956482dd3c70b8991f6f7654356339e6","versionType":"git"},{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"9006c116dd111d457bf5d074990210f70a4ad2c8","versionType":"git"},{"version":"f6104e9ae04462523c372928b1173766a771ef95","status":"affected","versionType":"git"},{"version":"7f8e401f9e612df2a95c1ef76217c00181389bb5","status":"affected","versionType":"git"},{"version":"c712ed63e9b33d9a282fbd92ce25c64918c3129f","status":"affected","versionType":"git"},{"version":"9a8863e8a8def9d88583cd9c60db38a008e6b8cf","status":"affected","versionType":"git"},{"version":"3.16.60","status":"affected","lessThan":"3.17","versionType":"semver"},{"version":"4.16.6","status":"affected","lessThan":"4.17","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/l2tp/l2tp_debugfs.c","net/l2tp/l2tp_ppp.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.17","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.10","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/l2tp/l2tp_debugfs.c","net/l2tp/l2tp_ppp.c"]}],"references":["https://git.kernel.org/stable/c/c38b723858a51d6ca4e56470b9f1087f23276772","https://git.kernel.org/stable/c/bd897e414451fb34dfdf08b31899180e5ab7149b","https://git.kernel.org/stable/c/bdf83613781956cc39798ed08321f74ab0467f4d","https://git.kernel.org/stable/c/8c4fde01bcf91f22b9c7ded8c3e14addd7ddd500","https://git.kernel.org/stable/c/ebe2774e956482dd3c70b8991f6f7654356339e6","https://git.kernel.org/stable/c/9006c116dd111d457bf5d074990210f70a4ad2c8"],"weaknesses":[],"ingestedAt":"2026-10-30T12:48:04.825Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74735.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74735","state":"PUBLISHED","datePublished":"2026-08-26T14:36:49.352Z","dateUpdated":"2026-10-30T12:30:27.082Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.930Z"},"containers":{"cna":{"title":"l2tp: fix tunnel and session refcount leak on seq_file release","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nl2tp: fix tunnel and session refcount leak on seq_file release\n\nIn pppol2tp_proc_open() and l2tp_dfs_seq_open(), iteration state\n(pd->tunnel and pd->session) is kept in seq_file private data to allow\niteration across multiple read() system calls.\n\nHowever, if userspace closes /proc/net/pppol2tp or /sys/kernel/debug/l2tp/tunnels\nbefore reading to end-of-file (EOF), any tunnel or session reference stored in\npd->tunnel / pd->session is left un-dropped when seq_file private data is freed.\n\nFix this by dropping any remaining pd->tunnel and pd->session references in\npppol2tp_proc_release() and l2tp_dfs_seq_release() when closing the file."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"c38b723858a51d6ca4e56470b9f1087f23276772","versionType":"git"},{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"bd897e414451fb34dfdf08b31899180e5ab7149b","versionType":"git"},{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"bdf83613781956cc39798ed08321f74ab0467f4d","versionType":"git"},{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"8c4fde01bcf91f22b9c7ded8c3e14addd7ddd500","versionType":"git"},{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"ebe2774e956482dd3c70b8991f6f7654356339e6","versionType":"git"},{"version":"0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443","status":"affected","lessThan":"9006c116dd111d457bf5d074990210f70a4ad2c8","versionType":"git"},{"version":"f6104e9ae04462523c372928b1173766a771ef95","status":"affected","versionType":"git"},{"version":"7f8e401f9e612df2a95c1ef76217c00181389bb5","status":"affected","versionType":"git"},{"version":"c712ed63e9b33d9a282fbd92ce25c64918c3129f","status":"affected","versionType":"git"},{"version":"9a8863e8a8def9d88583cd9c60db38a008e6b8cf","status":"affected","versionType":"git"},{"version":"3.16.60","status":"affected","lessThan":"3.17","versionType":"semver"},{"version":"4.16.6","status":"affected","lessThan":"4.17","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/l2tp/l2tp_debugfs.c","net/l2tp/l2tp_ppp.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.17","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.10","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/l2tp/l2tp_debugfs.c","net/l2tp/l2tp_ppp.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/c38b723858a51d6ca4e56470b9f1087f23276772"},{"url":"https://git.kernel.org/stable/c/bd897e414451fb34dfdf08b31899180e5ab7149b"},{"url":"https://git.kernel.org/stable/c/bdf83613781956cc39798ed08321f74ab0467f4d"},{"url":"https://git.kernel.org/stable/c/8c4fde01bcf91f22b9c7ded8c3e14addd7ddd500"},{"url":"https://git.kernel.org/stable/c/ebe2774e956482dd3c70b8991f6f7654356339e6"},{"url":"https://git.kernel.org/stable/c/9006c116dd111d457bf5d074990210f70a4ad2c8"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:30:27.082Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.12.111"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"7.1.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16.60"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.16.60"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16.6"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}