{"id":"CVE-2026-74577","title":"net: mpls: initialize rtm_tos in mpls_getroute()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mpls: initialize rtm_tos in mpls_getroute()\n\nmpls_getroute() builds the RTM_NEWROUTE reply to an RTM_GETROUTE\nrequest by filling a struct rtmsg allocated from an s…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 248718fd88b146d8bdc7610ecd1eb4cd16e0b5a1","Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 466b474a8deb0c93b5280c6d261e5eda6482eca7","Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < ba56f88aab18d982f2a21f11390f4d8a8897782a","Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 95651461cf77cc6590fa08c87667717e5dcfa55d","Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 1fea5ff0eb4aa7e951bb3d380248566c473aa377","Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < a5cdd2407dd890f741f59b8367e4c6c101cce154","Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 2dc2fffc704a4365cae1aae078ba62223aaeff93","Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 295dd295e2137e10e9a5b1891d97e0f08de76f03","Linux 4.13"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-06T16:59:42.740510Z"},"published":"2026-08-15","updated":"2026-11-06","sourceUpdated":"2026-11-06T17:05:48.538Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-74577","references":[{"url":"https://git.kernel.org/stable/c/248718fd88b146d8bdc7610ecd1eb4cd16e0b5a1"},{"url":"https://git.kernel.org/stable/c/466b474a8deb0c93b5280c6d261e5eda6482eca7"},{"url":"https://git.kernel.org/stable/c/ba56f88aab18d982f2a21f11390f4d8a8897782a"},{"url":"https://git.kernel.org/stable/c/95651461cf77cc6590fa08c87667717e5dcfa55d"},{"url":"https://git.kernel.org/stable/c/1fea5ff0eb4aa7e951bb3d380248566c473aa377"},{"url":"https://git.kernel.org/stable/c/a5cdd2407dd890f741f59b8367e4c6c101cce154"},{"url":"https://git.kernel.org/stable/c/2dc2fffc704a4365cae1aae078ba62223aaeff93"},{"url":"https://git.kernel.org/stable/c/295dd295e2137e10e9a5b1891d97e0f08de76f03"}],"tags":["cve.org"],"epss":0.00165,"epssPercentile":0.05778,"ingestedAt":"2026-11-06T18:00:12.546Z","slug":"CVE-2026-74577","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet: mpls: initialize rtm_tos in mpls_getroute()\n\nmpls_getroute() builds the RTM_NEWROUTE reply to an RTM_GETROUTE\nrequest by filling a struct rtmsg allocated from an skb whose data\narea is not zeroed (alloc_skb(NLMSG_GOODSIZE, ...)). It sets every\nfield of the header except rtm_tos:\n\n\tr = nlmsg_data(nlh);\n\tr->rtm_family\t = AF_MPLS;\n\tr->rtm_dst_len\t= 20;\n\tr->rtm_src_len\t= 0;\n\tr->rtm_table\t= RT_TABLE_MAIN;\n\tr->rtm_type\t= RTN_UNICAST;\n\tr->rtm_scope\t= RT_SCOPE_UNIVERSE;\n\tr->rtm_protocol = rt->rt_protocol;\n\tr->rtm_flags\t= 0;\n\nstruct rtmsg has no padding, so the one uninitialised byte rtm_tos\n(offset 3) is copied straight to user space on recvmsg(), leaking a\nbyte of uninitialised heap memory. This is in contrast to\nmpls_dump_route(), which fills the very same header and does set\nrtm_tos = 0.\n\nInitialize rtm_tos to 0, matching mpls_dump_route().\n\nReproduced with KMSAN by adding an MPLS route and issuing a\nnon-RTM_F_FIB_MATCH RTM_GETROUTE for its label:\n\n  BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x36c/0x33f0\n   _copy_to_iter+0x36c/0x33f0\n   __skb_datagram_iter+0x196/0x12c0\n   skb_copy_datagram_iter+0x5b/0x210\n   netlink_recvmsg+0x37b/0xef0\n   ...\n  Uninit was created at:\n   __alloc_skb+0x8ca/0x10e0\n   mpls_getroute+0x1280/0x3a40\n   rtnetlink_rcv_msg+0x1138/0x15a0\n   ...\n  Byte 19 of 64 is uninitialized\n\n(byte 19 = nlmsghdr(16) + rtmsg offset 3 = rtm_tos)\n\n## Affected\n\n- `Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 248718fd88b146d8bdc7610ecd1eb4cd16e0b5a1`\n- `Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 466b474a8deb0c93b5280c6d261e5eda6482eca7`\n- `Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < ba56f88aab18d982f2a21f11390f4d8a8897782a`\n- `Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 95651461cf77cc6590fa08c87667717e5dcfa55d`\n- `Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 1fea5ff0eb4aa7e951bb3d380248566c473aa377`\n- `Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < a5cdd2407dd890f741f59b8367e4c6c101cce154`\n- `Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 2dc2fffc704a4365cae1aae078ba62223aaeff93`\n- `Linux >= 397fc9e5cefee0c33b86811fbddb0decb7288c52 < 295dd295e2137e10e9a5b1891d97e0f08de76f03`\n- `Linux 4.13`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}