{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "397fc9e5cefee0c33b86811fbddb0decb7288c52"
            },
            {
              "fixed": "248718fd88b146d8bdc7610ecd1eb4cd16e0b5a1"
            },
            {
              "fixed": "466b474a8deb0c93b5280c6d261e5eda6482eca7"
            },
            {
              "fixed": "ba56f88aab18d982f2a21f11390f4d8a8897782a"
            },
            {
              "fixed": "95651461cf77cc6590fa08c87667717e5dcfa55d"
            },
            {
              "fixed": "1fea5ff0eb4aa7e951bb3d380248566c473aa377"
            },
            {
              "fixed": "a5cdd2407dd890f741f59b8367e4c6c101cce154"
            },
            {
              "fixed": "2dc2fffc704a4365cae1aae078ba62223aaeff93"
            },
            {
              "fixed": "295dd295e2137e10e9a5b1891d97e0f08de76f03"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.13.0"
            },
            {
              "fixed": "5.10.265"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "5.11.0"
            },
            {
              "fixed": "5.15.216"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "5.16.0"
            },
            {
              "fixed": "6.1.183"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.2.0"
            },
            {
              "fixed": "6.6.151"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.7.0"
            },
            {
              "fixed": "6.12.103"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.44"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.1.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74577.json"
  },
  "details": "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 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-\u003ertm_family\t = AF_MPLS;\n\tr-\u003ertm_dst_len\t= 20;\n\tr-\u003ertm_src_len\t= 0;\n\tr-\u003ertm_table\t= RT_TABLE_MAIN;\n\tr-\u003ertm_type\t= RTN_UNICAST;\n\tr-\u003ertm_scope\t= RT_SCOPE_UNIVERSE;\n\tr-\u003ertm_protocol = rt-\u003ert_protocol;\n\tr-\u003ertm_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)",
  "id": "CVE-2026-74577",
  "modified": "2026-08-21T03:30:39.312058573Z",
  "published": "2026-08-15T12:28:14.408Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1fea5ff0eb4aa7e951bb3d380248566c473aa377"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/248718fd88b146d8bdc7610ecd1eb4cd16e0b5a1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/295dd295e2137e10e9a5b1891d97e0f08de76f03"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2dc2fffc704a4365cae1aae078ba62223aaeff93"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/466b474a8deb0c93b5280c6d261e5eda6482eca7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/95651461cf77cc6590fa08c87667717e5dcfa55d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a5cdd2407dd890f741f59b8367e4c6c101cce154"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ba56f88aab18d982f2a21f11390f4d8a8897782a"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74577.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74577"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "summary": "net: mpls: initialize rtm_tos in mpls_getroute()"
}