FKIE_CVE-2026-74577

Vulnerability from fkie_nvd - Published: 2026-08-15 13:18 - Updated: 2026-08-19 17:21
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: net: mpls: initialize rtm_tos in mpls_getroute() mpls_getroute() builds the RTM_NEWROUTE reply to an RTM_GETROUTE request by filling a struct rtmsg allocated from an skb whose data area is not zeroed (alloc_skb(NLMSG_GOODSIZE, ...)). It sets every field of the header except rtm_tos: r = nlmsg_data(nlh); r->rtm_family = AF_MPLS; r->rtm_dst_len = 20; r->rtm_src_len = 0; r->rtm_table = RT_TABLE_MAIN; r->rtm_type = RTN_UNICAST; r->rtm_scope = RT_SCOPE_UNIVERSE; r->rtm_protocol = rt->rt_protocol; r->rtm_flags = 0; struct rtmsg has no padding, so the one uninitialised byte rtm_tos (offset 3) is copied straight to user space on recvmsg(), leaking a byte of uninitialised heap memory. This is in contrast to mpls_dump_route(), which fills the very same header and does set rtm_tos = 0. Initialize rtm_tos to 0, matching mpls_dump_route(). Reproduced with KMSAN by adding an MPLS route and issuing a non-RTM_F_FIB_MATCH RTM_GETROUTE for its label: BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x36c/0x33f0 _copy_to_iter+0x36c/0x33f0 __skb_datagram_iter+0x196/0x12c0 skb_copy_datagram_iter+0x5b/0x210 netlink_recvmsg+0x37b/0xef0 ... Uninit was created at: __alloc_skb+0x8ca/0x10e0 mpls_getroute+0x1280/0x3a40 rtnetlink_rcv_msg+0x1138/0x15a0 ... Byte 19 of 64 is uninitialized (byte 19 = nlmsghdr(16) + rtmsg offset 3 = rtm_tos)
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1fea5ff0eb4aa7e951bb3d380248566c473aa377
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/248718fd88b146d8bdc7610ecd1eb4cd16e0b5a1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/295dd295e2137e10e9a5b1891d97e0f08de76f03
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2dc2fffc704a4365cae1aae078ba62223aaeff93
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/466b474a8deb0c93b5280c6d261e5eda6482eca7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/95651461cf77cc6590fa08c87667717e5dcfa55d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a5cdd2407dd890f741f59b8367e4c6c101cce154
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ba56f88aab18d982f2a21f11390f4d8a8897782a
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/mpls/af_mpls.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "248718fd88b146d8bdc7610ecd1eb4cd16e0b5a1",
              "status": "affected",
              "version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
              "versionType": "git"
            },
            {
              "lessThan": "466b474a8deb0c93b5280c6d261e5eda6482eca7",
              "status": "affected",
              "version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
              "versionType": "git"
            },
            {
              "lessThan": "ba56f88aab18d982f2a21f11390f4d8a8897782a",
              "status": "affected",
              "version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
              "versionType": "git"
            },
            {
              "lessThan": "95651461cf77cc6590fa08c87667717e5dcfa55d",
              "status": "affected",
              "version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
              "versionType": "git"
            },
            {
              "lessThan": "1fea5ff0eb4aa7e951bb3d380248566c473aa377",
              "status": "affected",
              "version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
              "versionType": "git"
            },
            {
              "lessThan": "a5cdd2407dd890f741f59b8367e4c6c101cce154",
              "status": "affected",
              "version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
              "versionType": "git"
            },
            {
              "lessThan": "2dc2fffc704a4365cae1aae078ba62223aaeff93",
              "status": "affected",
              "version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
              "versionType": "git"
            },
            {
              "lessThan": "295dd295e2137e10e9a5b1891d97e0f08de76f03",
              "status": "affected",
              "version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/mpls/af_mpls.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.13"
            },
            {
              "lessThan": "4.13",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.265",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.216",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.183",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.151",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.103",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.44",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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",
  "lastModified": "2026-08-19T17:21:11.870",
  "metrics": {},
  "published": "2026-08-15T13:18:03.430",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/1fea5ff0eb4aa7e951bb3d380248566c473aa377"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/248718fd88b146d8bdc7610ecd1eb4cd16e0b5a1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/295dd295e2137e10e9a5b1891d97e0f08de76f03"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2dc2fffc704a4365cae1aae078ba62223aaeff93"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/466b474a8deb0c93b5280c6d261e5eda6482eca7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/95651461cf77cc6590fa08c87667717e5dcfa55d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a5cdd2407dd890f741f59b8367e4c6c101cce154"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ba56f88aab18d982f2a21f11390f4d8a8897782a"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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