CVE-2026-74577 (GCVE-0-2026-74577)

Vulnerability from cvelistv5 – Published: 2026-08-15 12:28 – Updated: 2026-08-17 05:22
VLAI
Title
net: mpls: initialize rtm_tos in mpls_getroute()
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)
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 397fc9e5cefee0c33b86811fbddb0decb7288c52 , < 95651461cf77cc6590fa08c87667717e5dcfa55d (git)
Affected: 397fc9e5cefee0c33b86811fbddb0decb7288c52 , < 1fea5ff0eb4aa7e951bb3d380248566c473aa377 (git)
Affected: 397fc9e5cefee0c33b86811fbddb0decb7288c52 , < a5cdd2407dd890f741f59b8367e4c6c101cce154 (git)
Affected: 397fc9e5cefee0c33b86811fbddb0decb7288c52 , < 2dc2fffc704a4365cae1aae078ba62223aaeff93 (git)
Affected: 397fc9e5cefee0c33b86811fbddb0decb7288c52 , < 295dd295e2137e10e9a5b1891d97e0f08de76f03 (git)
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Linux Linux Affected: 4.13
Unaffected: 0 , < 4.13 (semver)
Unaffected: 6.6.151 , ≤ 6.6.* (semver)
Unaffected: 6.12.103 , ≤ 6.12.* (semver)
Unaffected: 6.18.44 , ≤ 6.18.* (semver)
Unaffected: 7.1.8 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/mpls/af_mpls.c"
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              "versionType": "git"
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              "versionType": "git"
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          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "4.13"
            },
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              "lessThan": "4.13",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.151",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "6.12.103",
              "versionType": "semver"
            },
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              "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"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.151",
                  "versionStartIncluding": "4.13",
                  "vulnerable": true
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.44",
                  "versionStartIncluding": "4.13",
                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      "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)"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:22:07.878Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/95651461cf77cc6590fa08c87667717e5dcfa55d"
        },
        {
          "url": "https://git.kernel.org/stable/c/1fea5ff0eb4aa7e951bb3d380248566c473aa377"
        },
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        },
        {
          "url": "https://git.kernel.org/stable/c/2dc2fffc704a4365cae1aae078ba62223aaeff93"
        },
        {
          "url": "https://git.kernel.org/stable/c/295dd295e2137e10e9a5b1891d97e0f08de76f03"
        }
      ],
      "title": "net: mpls: initialize rtm_tos in mpls_getroute()",
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      }
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74577",
    "datePublished": "2026-08-15T12:28:14.408Z",
    "dateReserved": "2026-08-15T05:44:03.917Z",
    "dateUpdated": "2026-08-17T05:22:07.878Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-74577",
      "date": "2026-08-18",
      "epss": "0.00157",
      "percentile": "0.05364"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-74577\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-08-15T13:18:03.430\",\"lastModified\":\"2026-08-17T06:19:56.173\",\"vulnStatus\":\"Received\",\"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)\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/mpls/af_mpls.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"397fc9e5cefee0c33b86811fbddb0decb7288c52\",\"lessThan\":\"95651461cf77cc6590fa08c87667717e5dcfa55d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"397fc9e5cefee0c33b86811fbddb0decb7288c52\",\"lessThan\":\"1fea5ff0eb4aa7e951bb3d380248566c473aa377\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"397fc9e5cefee0c33b86811fbddb0decb7288c52\",\"lessThan\":\"a5cdd2407dd890f741f59b8367e4c6c101cce154\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"397fc9e5cefee0c33b86811fbddb0decb7288c52\",\"lessThan\":\"2dc2fffc704a4365cae1aae078ba62223aaeff93\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"397fc9e5cefee0c33b86811fbddb0decb7288c52\",\"lessThan\":\"295dd295e2137e10e9a5b1891d97e0f08de76f03\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/mpls/af_mpls.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"4.13\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"4.13\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.151\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.103\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.44\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.8\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/1fea5ff0eb4aa7e951bb3d380248566c473aa377\",\"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/95651461cf77cc6590fa08c87667717e5dcfa55d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a5cdd2407dd890f741f59b8367e4c6c101cce154\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "suse_vex": {
      "aggregate_severity": "not set",
      "current_release_date": "2026-08-15T16:24:31Z",
      "cve": "CVE-2026-74577",
      "id": "CVE-2026-74577",
      "initial_release_date": "2026-08-15T16:24:31Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-74577",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-74577.json",
      "version": "2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.