CVE-2026-43029 (GCVE-0-2026-43029)

Vulnerability from cvelistv5 – Published: 2026-05-01 14:15 – Updated: 2026-05-03 05:46
VLAI?
Title
mptcp: fix soft lockup in mptcp_recvmsg()
Summary
In the Linux kernel, the following vulnerability has been resolved: mptcp: fix soft lockup in mptcp_recvmsg() syzbot reported a soft lockup in mptcp_recvmsg() [0]. When receiving data with MSG_PEEK | MSG_WAITALL flags, the skb is not removed from the sk_receive_queue. This causes sk_wait_data() to always find available data and never perform actual waiting, leading to a soft lockup. Fix this by adding a 'last' parameter to track the last peeked skb. This allows sk_wait_data() to make informed waiting decisions and prevent infinite loops when MSG_PEEK is used. [0]: watchdog: BUG: soft lockup - CPU#2 stuck for 156s! [server:1963] Modules linked in: CPU: 2 UID: 0 PID: 1963 Comm: server Not tainted 6.19.0-rc8 #61 PREEMPT(none) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:sk_wait_data+0x15/0x190 Code: 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 56 41 55 41 54 49 89 f4 55 48 89 d5 53 48 89 fb <48> 83 ec 30 65 48 8b 05 17 a4 6b 01 48 89 44 24 28 31 c0 65 48 8b RSP: 0018:ffffc90000603ca0 EFLAGS: 00000246 RAX: 0000000000000000 RBX: ffff888102bf0800 RCX: 0000000000000001 RDX: 0000000000000000 RSI: ffffc90000603d18 RDI: ffff888102bf0800 RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000101 R10: 0000000000000000 R11: 0000000000000075 R12: ffffc90000603d18 R13: ffff888102bf0800 R14: ffff888102bf0800 R15: 0000000000000000 FS: 00007f6e38b8c4c0(0000) GS:ffff8881b877e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055aa7bff1680 CR3: 0000000105cbe000 CR4: 00000000000006f0 Call Trace: <TASK> mptcp_recvmsg+0x547/0x8c0 net/mptcp/protocol.c:2329 inet_recvmsg+0x11f/0x130 net/ipv4/af_inet.c:891 sock_recvmsg+0x94/0xc0 net/socket.c:1100 __sys_recvfrom+0xb2/0x130 net/socket.c:2256 __x64_sys_recvfrom+0x1f/0x30 net/socket.c:2267 do_syscall_64+0x59/0x2d0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x76/0x7e arch/x86/entry/entry_64.S:131 RIP: 0033:0x7f6e386a4a1d Code: 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 8d 05 f1 de 2c 00 41 89 ca 8b 00 85 c0 75 20 45 31 c9 45 31 c0 b8 2d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 6b f3 c3 66 0f 1f 84 00 00 00 00 00 41 56 41 RSP: 002b:00007ffc3c4bb078 EFLAGS: 00000246 ORIG_RAX: 000000000000002d RAX: ffffffffffffffda RBX: 000000000000861e RCX: 00007f6e386a4a1d RDX: 00000000000003ff RSI: 00007ffc3c4bb150 RDI: 0000000000000004 RBP: 00007ffc3c4bb570 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000103 R11: 0000000000000246 R12: 00005605dbc00be0 R13: 00007ffc3c4bb650 R14: 0000000000000000 R15: 0000000000000000 </TASK>
Severity ?
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 8e04ce45a8db7a080220e86e249198fa676b83dc , < 58b58b9ba89c43914eea90c18928e51852d10c24 (git)
Affected: 8e04ce45a8db7a080220e86e249198fa676b83dc , < de3c248d1b69eaefa2d5b3da4005936dcf590f1b (git)
Affected: 8e04ce45a8db7a080220e86e249198fa676b83dc , < 5dd8025a49c268ab6b94d978532af3ad341132a7 (git)
Affected: 49888b3b457b801282b44c246d289c56e2f2a55b (git)
Affected: 0206a9341e652167c610dcd79f3d4e9e8153984c (git)
Affected: 7d6d10eee01edc9c20850ea75cf8273dc1170921 (git)
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    Linux Linux Affected: 6.18
Unaffected: 0 , < 6.18 (semver)
Unaffected: 6.18.22 , ≤ 6.18.* (semver)
Unaffected: 6.19.12 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/mptcp/protocol.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "versionType": "git"
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              "versionType": "git"
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              "versionType": "git"
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              "version": "49888b3b457b801282b44c246d289c56e2f2a55b",
              "versionType": "git"
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            {
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              "version": "0206a9341e652167c610dcd79f3d4e9e8153984c",
              "versionType": "git"
            },
            {
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              "version": "7d6d10eee01edc9c20850ea75cf8273dc1170921",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/mptcp/protocol.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.18"
            },
            {
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.18.22",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "6.19.12",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.22",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                },
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix soft lockup in mptcp_recvmsg()\n\nsyzbot reported a soft lockup in mptcp_recvmsg() [0].\n\nWhen receiving data with MSG_PEEK | MSG_WAITALL flags, the skb is not\nremoved from the sk_receive_queue. This causes sk_wait_data() to always\nfind available data and never perform actual waiting, leading to a soft\nlockup.\n\nFix this by adding a \u0027last\u0027 parameter to track the last peeked skb.\nThis allows sk_wait_data() to make informed waiting decisions and prevent\ninfinite loops when MSG_PEEK is used.\n\n[0]:\nwatchdog: BUG: soft lockup - CPU#2 stuck for 156s! [server:1963]\nModules linked in:\nCPU: 2 UID: 0 PID: 1963 Comm: server Not tainted 6.19.0-rc8 #61 PREEMPT(none)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014\nRIP: 0010:sk_wait_data+0x15/0x190\nCode: 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 56 41 55 41 54 49 89 f4 55 48 89 d5 53 48 89 fb \u003c48\u003e 83 ec 30 65 48 8b 05 17 a4 6b 01 48 89 44 24 28 31 c0 65 48 8b\nRSP: 0018:ffffc90000603ca0 EFLAGS: 00000246\nRAX: 0000000000000000 RBX: ffff888102bf0800 RCX: 0000000000000001\nRDX: 0000000000000000 RSI: ffffc90000603d18 RDI: ffff888102bf0800\nRBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000101\nR10: 0000000000000000 R11: 0000000000000075 R12: ffffc90000603d18\nR13: ffff888102bf0800 R14: ffff888102bf0800 R15: 0000000000000000\nFS:  00007f6e38b8c4c0(0000) GS:ffff8881b877e000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 000055aa7bff1680 CR3: 0000000105cbe000 CR4: 00000000000006f0\nCall Trace:\n \u003cTASK\u003e\n mptcp_recvmsg+0x547/0x8c0 net/mptcp/protocol.c:2329\n inet_recvmsg+0x11f/0x130 net/ipv4/af_inet.c:891\n sock_recvmsg+0x94/0xc0 net/socket.c:1100\n __sys_recvfrom+0xb2/0x130 net/socket.c:2256\n __x64_sys_recvfrom+0x1f/0x30 net/socket.c:2267\n do_syscall_64+0x59/0x2d0 arch/x86/entry/syscall_64.c:94\n entry_SYSCALL_64_after_hwframe+0x76/0x7e arch/x86/entry/entry_64.S:131\nRIP: 0033:0x7f6e386a4a1d\nCode: 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 8d 05 f1 de 2c 00 41 89 ca 8b 00 85 c0 75 20 45 31 c9 45 31 c0 b8 2d 00 00 00 0f 05 \u003c48\u003e 3d 00 f0 ff ff 77 6b f3 c3 66 0f 1f 84 00 00 00 00 00 41 56 41\nRSP: 002b:00007ffc3c4bb078 EFLAGS: 00000246 ORIG_RAX: 000000000000002d\nRAX: ffffffffffffffda RBX: 000000000000861e RCX: 00007f6e386a4a1d\nRDX: 00000000000003ff RSI: 00007ffc3c4bb150 RDI: 0000000000000004\nRBP: 00007ffc3c4bb570 R08: 0000000000000000 R09: 0000000000000000\nR10: 0000000000000103 R11: 0000000000000246 R12: 00005605dbc00be0\nR13: 00007ffc3c4bb650 R14: 0000000000000000 R15: 0000000000000000\n \u003c/TASK\u003e"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-03T05:46:11.595Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/58b58b9ba89c43914eea90c18928e51852d10c24"
        },
        {
          "url": "https://git.kernel.org/stable/c/de3c248d1b69eaefa2d5b3da4005936dcf590f1b"
        },
        {
          "url": "https://git.kernel.org/stable/c/5dd8025a49c268ab6b94d978532af3ad341132a7"
        }
      ],
      "title": "mptcp: fix soft lockup in mptcp_recvmsg()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43029",
    "datePublished": "2026-05-01T14:15:29.885Z",
    "dateReserved": "2026-05-01T14:12:55.976Z",
    "dateUpdated": "2026-05-03T05:46:11.595Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-43029",
      "date": "2026-05-04",
      "epss": "0.00038",
      "percentile": "0.11092"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-43029\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-05-01T15:16:47.427\",\"lastModified\":\"2026-05-03T07:16:22.747\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nmptcp: fix soft lockup in mptcp_recvmsg()\\n\\nsyzbot reported a soft lockup in mptcp_recvmsg() [0].\\n\\nWhen receiving data with MSG_PEEK | MSG_WAITALL flags, the skb is not\\nremoved from the sk_receive_queue. This causes sk_wait_data() to always\\nfind available data and never perform actual waiting, leading to a soft\\nlockup.\\n\\nFix this by adding a \u0027last\u0027 parameter to track the last peeked skb.\\nThis allows sk_wait_data() to make informed waiting decisions and prevent\\ninfinite loops when MSG_PEEK is used.\\n\\n[0]:\\nwatchdog: BUG: soft lockup - CPU#2 stuck for 156s! [server:1963]\\nModules linked in:\\nCPU: 2 UID: 0 PID: 1963 Comm: server Not tainted 6.19.0-rc8 #61 PREEMPT(none)\\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014\\nRIP: 0010:sk_wait_data+0x15/0x190\\nCode: 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 56 41 55 41 54 49 89 f4 55 48 89 d5 53 48 89 fb \u003c48\u003e 83 ec 30 65 48 8b 05 17 a4 6b 01 48 89 44 24 28 31 c0 65 48 8b\\nRSP: 0018:ffffc90000603ca0 EFLAGS: 00000246\\nRAX: 0000000000000000 RBX: ffff888102bf0800 RCX: 0000000000000001\\nRDX: 0000000000000000 RSI: ffffc90000603d18 RDI: ffff888102bf0800\\nRBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000101\\nR10: 0000000000000000 R11: 0000000000000075 R12: ffffc90000603d18\\nR13: ffff888102bf0800 R14: ffff888102bf0800 R15: 0000000000000000\\nFS:  00007f6e38b8c4c0(0000) GS:ffff8881b877e000(0000) knlGS:0000000000000000\\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\\nCR2: 000055aa7bff1680 CR3: 0000000105cbe000 CR4: 00000000000006f0\\nCall Trace:\\n \u003cTASK\u003e\\n mptcp_recvmsg+0x547/0x8c0 net/mptcp/protocol.c:2329\\n inet_recvmsg+0x11f/0x130 net/ipv4/af_inet.c:891\\n sock_recvmsg+0x94/0xc0 net/socket.c:1100\\n __sys_recvfrom+0xb2/0x130 net/socket.c:2256\\n __x64_sys_recvfrom+0x1f/0x30 net/socket.c:2267\\n do_syscall_64+0x59/0x2d0 arch/x86/entry/syscall_64.c:94\\n entry_SYSCALL_64_after_hwframe+0x76/0x7e arch/x86/entry/entry_64.S:131\\nRIP: 0033:0x7f6e386a4a1d\\nCode: 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 8d 05 f1 de 2c 00 41 89 ca 8b 00 85 c0 75 20 45 31 c9 45 31 c0 b8 2d 00 00 00 0f 05 \u003c48\u003e 3d 00 f0 ff ff 77 6b f3 c3 66 0f 1f 84 00 00 00 00 00 41 56 41\\nRSP: 002b:00007ffc3c4bb078 EFLAGS: 00000246 ORIG_RAX: 000000000000002d\\nRAX: ffffffffffffffda RBX: 000000000000861e RCX: 00007f6e386a4a1d\\nRDX: 00000000000003ff RSI: 00007ffc3c4bb150 RDI: 0000000000000004\\nRBP: 00007ffc3c4bb570 R08: 0000000000000000 R09: 0000000000000000\\nR10: 0000000000000103 R11: 0000000000000246 R12: 00005605dbc00be0\\nR13: 00007ffc3c4bb650 R14: 0000000000000000 R15: 0000000000000000\\n \u003c/TASK\u003e\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":3.6}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/58b58b9ba89c43914eea90c18928e51852d10c24\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/5dd8025a49c268ab6b94d978532af3ad341132a7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/de3c248d1b69eaefa2d5b3da4005936dcf590f1b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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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.