{"id":"CVE-2026-63803","revision":"04eb967f59914eaeb346a13de2e4c903","records":[{"revision":"04eb967f59914eaeb346a13de2e4c903","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-63803","aliases":[],"title":"hdlc_ppp: sync per-proto timers before freeing hdlc state","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nhdlc_ppp: sync per-proto timers before freeing hdlc state\n\nEach PPP control protocol (LCP/IPCP/IPV6CP) embedded in struct ppp\nregisters a timer via timer_setup(). That struct ppp is the\nhdlc->state allocation, which detach_hdlc_protocol() frees with kfree()\nin both teardown paths: unregister_hdlc_device() and the re-attach inside\nattach_hdlc_protocol().\n\nThe ppp proto never registered a .detach callback, so\ndetach_hdlc_protocol() performs no timer synchronization before the\nkfree(). The only cancel, timer_delete(&proto->timer) in ppp_cp_event(),\nis partial (it does not wait for a running callback) and only runs on the\n->CLOSED transition; ppp_stop()/ppp_close() do not sync either. A\nppp_timer callback already executing (blocked on ppp->lock) survives the\nkfree and then dereferences proto->state / ppp->lock in freed memory,\nleading to a use-after-free.\n\nFix this by adding a .detach helper that calls timer_shutdown_sync() on\nevery per-proto timer. detach_hdlc_protocol() invokes proto->detach(dev)\nbefore kfree(hdlc->state), so timer_shutdown_sync()\nnow runs on both free paths.\ntimer_shutdown_sync() is used instead of timer_delete_sync() because the\nkeepalive path re-arms the timer through add_timer()/mod_timer() and\nshutdown blocks any re-activation during teardown.\n\nInitialize the per-protocol timers in ppp_ioctl() when the protocol is\nattached, and remove the now-redundant timer_setup() from ppp_start(), so\nthat the timers are initialized exactly once at attach time and\nppp_timer_release() never operates on uninitialized timer_list\nstructures. attach_hdlc_protocol() uses kmalloc() (not kzalloc), so\nstruct ppp's protos[i].timer is uninitialized garbage until the first\ntimer_setup(); without this init-at-attach, attaching the PPP protocol\nwithout ever bringing the device up would leave timer_shutdown_sync()\noperating on uninitialized memory in .detach. Moving the init out of\nppp_start() (which only runs on NETDEV_UP) into the attach path makes the\ninitialization unconditional and avoids initializing the same timer_list\ntwice.\n\nThis bug was found by static analysis.","state":0,"publishedAt":"2026-07-19T12:02:08.574+00:00","modifiedAt":"2026-10-19T20:07:47.971+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"drivers/net/wan/hdlc_ppp.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"86d80a231bde4cfb64bfbfbfffd83056fc93628f\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"8308122bc9c065b1f376e081ed300129a2ac9545\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"ce8f9ddca0c9f217342a8b49efd309aa35b81a36\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"508a0139d3bf60f6a03d2fbfb63a89a9463d983a\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"c64dbef1c0fbd36f9530aa75112acdf6a6d3cfd8\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"5a84398101bf9f11e84b176343e4e3ba83e668c0\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"a594debfd4e7ec39413647458907f689ef57fd2f\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"c78a4e41ab5ead6193ad8a2dd92e8906bae659fa\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"drivers/net/wan/hdlc_ppp.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"2.6.12\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"2.6.12\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.261\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.211\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.177\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.144\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.95\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.38\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.1.3\",\n                            \"lessThanOrEqual\": \"7.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/86d80a231bde4cfb64bfbfbfffd83056fc93628f","https://git.kernel.org/stable/c/8308122bc9c065b1f376e081ed300129a2ac9545","https://git.kernel.org/stable/c/ce8f9ddca0c9f217342a8b49efd309aa35b81a36","https://git.kernel.org/stable/c/508a0139d3bf60f6a03d2fbfb63a89a9463d983a","https://git.kernel.org/stable/c/c64dbef1c0fbd36f9530aa75112acdf6a6d3cfd8","https://git.kernel.org/stable/c/5a84398101bf9f11e84b176343e4e3ba83e668c0","https://git.kernel.org/stable/c/a594debfd4e7ec39413647458907f689ef57fd2f","https://git.kernel.org/stable/c/c78a4e41ab5ead6193ad8a2dd92e8906bae659fa"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-63803","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-63803","identifiers":["CVE-2026-63803"]},"retained":false,"historicalAffected":[]}],"coverage":[]}