{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2021-47555", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-05-24T15:02:54.833Z", "datePublished": "2024-05-24T15:09:57.302Z", "dateUpdated": "2026-08-04T09:01:17.842Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-04T09:01:17.842Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: vlan: fix underflow for the real_dev refcnt\n\nInject error before dev_hold(real_dev) in register_vlan_dev(),\nand execute the following testcase:\n\nip link add dev dummy1 type dummy\nip link add name dummy1.100 link dummy1 type vlan id 100\nip link del dev dummy1\n\nWhen the dummy netdevice is removed, we will get a WARNING as following:\n\n=======================================================================\nrefcount_t: decrement hit 0; leaking memory.\nWARNING: CPU: 2 PID: 0 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0\n\nand an endless loop of:\n\n=======================================================================\nunregister_netdevice: waiting for dummy1 to become free. Usage count = -1073741824\n\nThat is because dev_put(real_dev) in vlan_dev_free() be called without\ndev_hold(real_dev) in register_vlan_dev(). It makes the refcnt of real_dev\nunderflow.\n\nMove the dev_hold(real_dev) to vlan_dev_init() which is the call-back of\nndo_init(). 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Usage count = -1073741824\n\nThat is because dev_put(real_dev) in vlan_dev_free() be called without\ndev_hold(real_dev) in register_vlan_dev(). It makes the refcnt of real_dev\nunderflow.\n\nMove the dev_hold(real_dev) to vlan_dev_init() which is the call-back of\nndo_init(). That makes dev_hold() and dev_put() for vlan's real_dev\nsymmetrical."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.4.163", "versionStartIncluding": "5.4.160"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.10.83", "versionStartIncluding": "5.10.80"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.15.6", "versionStartIncluding": "5.15.3"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionStartIncluding": "5.14.19"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-04T09:01:17.842Z"}}}, "cveMetadata": {"cveId": "CVE-2021-47555", "state": "PUBLISHED", "dateUpdated": "2026-08-04T09:01:17.842Z", "dateReserved": "2024-05-24T15:02:54.833Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2024-05-24T15:09:57.302Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["net/8021q/vlan.c", "net/8021q/vlan_dev.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "5e44178864b38dd70b877985abd7d86fdb95f27d", "status": "affected", "version": "700602b662d7eaa816b1a3cb0abe7a85de358fd4", "versionType": "git"}, {"lessThan": "6e800ee43218a56acc93676bbb3d93b74779e555", "status": "affected", "version": "e04a7a84bb77f9cdf4475340fe931389bc72331c", "versionType": "git"}, {"lessThan": "f7fc72a508cf115c273a7a29350069def1041890", "status": "affected", "version": "21032425c36ff85f16e72ca92193a8c401e4acd5", "versionType": "git"}, {"lessThan": "01d9cc2dea3fde3bad6d27f464eff463496e2b00", "status": "affected", "version": "563bcbae3ba233c275c244bfce2efe12938f5363", "versionType": "git"}, {"status": "affected", "version": "fca96b3f852a1b369b7b2844ce357cd689879934", "versionType": "git"}, {"lessThan": "5.15", "status": "affected", "version": "5.14.19", "versionType": "semver"}]}, {"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["net/8021q/vlan.c", "net/8021q/vlan_dev.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "5.4.163", "status": "affected", "version": "5.4.160", "versionType": "semver"}, {"lessThan": "5.10.83", "status": "affected", "version": "5.10.80", "versionType": "semver"}, {"lessThan": "5.15.6", "status": "affected", "version": "5.15.3", "versionType": "semver"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "B23C9FD1-DA5D-41F5-8095-61EE3995E071", "versionEndExcluding": "5.4.163", "versionStartIncluding": "5.4.160", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "796E83A2-5253-4668-8475-92A87F819C3E", "versionEndExcluding": "5.10.83", "versionStartIncluding": "5.10.80", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "CC24A46F-AAF0-46A3-9255-D235078D50BC", "versionEndExcluding": "5.15", "versionStartIncluding": "5.14.19", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "2DC4F41E-7E5C-409A-9B7B-E32D1F806715", "versionEndExcluding": "5.15.6", "versionStartIncluding": "5.15.3", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:*", "matchCriteriaId": "357AA433-37E8-4323-BFB2-3038D6E4B414", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:*", "matchCriteriaId": "A73429BA-C2D9-4D0C-A75F-06A1CA8B3983", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: vlan: fix underflow for the real_dev refcnt\n\nInject error before dev_hold(real_dev) in register_vlan_dev(),\nand execute the following testcase:\n\nip link add dev dummy1 type dummy\nip link add name dummy1.100 link dummy1 type vlan id 100\nip link del dev dummy1\n\nWhen the dummy netdevice is removed, we will get a WARNING as following:\n\n=======================================================================\nrefcount_t: decrement hit 0; leaking memory.\nWARNING: CPU: 2 PID: 0 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0\n\nand an endless loop of:\n\n=======================================================================\nunregister_netdevice: waiting for dummy1 to become free. Usage count = -1073741824\n\nThat is because dev_put(real_dev) in vlan_dev_free() be called without\ndev_hold(real_dev) in register_vlan_dev(). It makes the refcnt of real_dev\nunderflow.\n\nMove the dev_hold(real_dev) to vlan_dev_init() which is the call-back of\nndo_init(). That makes dev_hold() and dev_put() for vlan's real_dev\nsymmetrical."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net: vlan: corrige el desbordamiento insuficiente para real_dev refcnt Inyecte el error antes de dev_hold(real_dev) en Register_vlan_dev() y ejecute el siguiente caso de prueba: ip link add dev dummy1 tipo dummy ip link add nombre dummy1.100 link dummy1 tipo vlan id 100 ip link del dev dummy1 Cuando se elimina el dispositivo de red ficticio, recibiremos una ADVERTENCIA como la siguiente: ===================== ==================================================== = refcount_t: decremento hit 0; p\u00e9rdida de memoria. ADVERTENCIA: CPU: 2 PID: 0 en lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0 y un bucle sin fin de: ======================== ================================================= unregister_netdevice: esperando que el dummy1 quede libre. Recuento de uso = -1073741824 Esto se debe a que dev_put(real_dev) en vlan_dev_free() se llama sin dev_hold(real_dev) en Register_vlan_dev(). Hace que el refcnt de real_dev se desborde. Mueva dev_hold(real_dev) a vlan_dev_init() que es la devoluci\u00f3n de llamada de ndo_init(). Eso hace que dev_hold() y dev_put() para real_dev de vlan sean sim\u00e9tricos."}], "id": "CVE-2021-47555", "lastModified": "2026-06-17T04:17:45.530", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "LOW", "baseScore": 4.4, "baseSeverity": "MEDIUM", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 2.5, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-47555", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2024-05-29T16:50:13.639283Z", "version": "2.0.3"}}]}, "published": "2024-05-24T15:15:20.237", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/01d9cc2dea3fde3bad6d27f464eff463496e2b00"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/5e44178864b38dd70b877985abd7d86fdb95f27d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6e800ee43218a56acc93676bbb3d93b74779e555"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f7fc72a508cf115c273a7a29350069def1041890"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/01d9cc2dea3fde3bad6d27f464eff463496e2b00"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/5e44178864b38dd70b877985abd7d86fdb95f27d"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6e800ee43218a56acc93676bbb3d93b74779e555"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f7fc72a508cf115c273a7a29350069def1041890"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-191"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: net: vlan: fix underflow for the real_dev refcnt", "id": "2283394", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2283394"}, "csaw": false, "cvss3": {"cvss3_base_score": "4.4", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L", "status": "draft"}, "cwe": "(CWE-911|CWE-124)", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nnet: vlan: fix underflow for the real_dev refcnt\nInject error before dev_hold(real_dev) in register_vlan_dev(),\nand execute the following testcase:\nip link add dev dummy1 type dummy\nip link add name dummy1.100 link dummy1 type vlan id 100\nip link del dev dummy1\nWhen the dummy netdevice is removed, we will get a WARNING as following:\n=======================================================================\nrefcount_t: decrement hit 0; leaking memory.\nWARNING: CPU: 2 PID: 0 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0\nand an endless loop of:\n=======================================================================\nunregister_netdevice: waiting for dummy1 to become free. Usage count = -1073741824\nThat is because dev_put(real_dev) in vlan_dev_free() be called without\ndev_hold(real_dev) in register_vlan_dev(). It makes the refcnt of real_dev\nunderflow.\nMove the dev_hold(real_dev) to vlan_dev_init() which is the call-back of\nndo_init(). That makes dev_hold() and dev_put() for vlan's real_dev\nsymmetrical."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability."}, "name": "CVE-2021-47555", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2024-05-24T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-47555\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-47555\nhttps://lore.kernel.org/linux-cve-announce/2024052443-CVE-2021-47555-3043@gregkh/T"], "threat_severity": "Low"}

{"created": "2025-07-13T11:32:02.980819+00:00", "updated": "2025-07-13T11:32:02.980894+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}