CVE-2021-47125

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Debido a que htb_graft_helper maneja adecuadamente el caso cuando new_q es NULL, y despu\u00e9s del parche anterior al omitir esta llamada, se crea una inconsistencia: dev_queue->qdisc seguir\u00e1 apuntando a la qdisc anterior, pero cl->parent->leaf.q apuntar\u00e1 a el nuevo (que ser\u00e1 noop_qdisc, porque new_q era NULL). El c\u00f3digo se basa en la suposici\u00f3n de que estos dos indicadores son iguales, por lo que puede provocar fugas de recuento. La soluci\u00f3n correcta es agregar una verificaci\u00f3n de puntero NULL para proteger qdisc_refcount_inc dentro de htb_parent_to_leaf_offload."}], "id": "CVE-2021-47125", "lastModified": "2026-06-17T04:16:35.013", "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"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-47125", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2024-03-18T15:30:07.969096Z", "version": "2.0.3"}}]}, "published": "2024-03-15T21:15:07.307", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/2411c02d03892a5057499f8102d0cc1e0f852416"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/944d671d5faa0d78980a3da5c0f04960ef1ad893"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/2411c02d03892a5057499f8102d0cc1e0f852416"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/944d671d5faa0d78980a3da5c0f04960ef1ad893"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-Other"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: sch_htb: fix refcount leak in htb_parent_to_leaf_offload", "id": "2269839", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2269839"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N", "status": "draft"}, "cwe": "CWE-402", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nsch_htb: fix refcount leak in htb_parent_to_leaf_offload\nThe commit ae81feb7338c (\"sch_htb: fix null pointer dereference\non a null new_q\") fixes a NULL pointer dereference bug, but it\nis not correct.\nBecause htb_graft_helper properly handles the case when new_q\nis NULL, and after the previous patch by skipping this call\nwhich creates an inconsistency : dev_queue->qdisc will still\npoint to the old qdisc, but cl->parent->leaf.q will point to\nthe new one (which will be noop_qdisc, because new_q was NULL).\nThe code is based on an assumption that these two pointers are\nthe same, so it can lead to refcount leaks.\nThe correct fix is to add a NULL pointer check to protect\nqdisc_refcount_inc inside htb_parent_to_leaf_offload.", "A vulnerability was found in the Linux kernel. The sch_htb component caused reference count leaks due to inconsistent handling of NULL pointers, leading to mismatched queue pointers."], "mitigation": {"lang": "en:us", "value": "Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible."}, "name": "CVE-2021-47125", "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": "2024-03-15T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-47125\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-47125\nhttps://lore.kernel.org/linux-cve-announce/2024031511-CVE-2021-47125-9c33@gregkh/T/#u"], "threat_severity": "Moderate"}

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