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The max page sharing of Kernel Samepage Merging (KSM), added in Linux kernel version 4.4.0-96.119, can create a side channel. When the attacker and the victim share the same host and the default setting of KSM is \"max page sharing=256\", it is possible for the attacker to time the unmap to merge with the victim's page. The unmapping time depends on whether it merges with the victim's page and additional physical pages are created beyond the KSM's \"max page share\". 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It should be carefully tested prior to deployment:\n\n- Deactivation of memory deduplication \n\nDeactivating memory deduplication will effectively mitigate all attack vectors. This measure unfortunately eliminates all the highly appreciated benefits of memory deduplication, namely the increase of operational cost-effectiveness through inter-VM memory sharing. This will cause an increase in the amount of memory required and in some situations may adversely impact performance (e.g. due to slower swap space being used). It is recommended that customers test this workaround before using it in production. See https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/virtualization_tuning_and_optimization_guide/sect-ksm-deactivating_ksm for how to disable KSM from Red Hat Enterprise Linux 6 and newer.\n\n- Disabling services and firewall rules.\n\nThe attack uses the response time of services on the system. By limiting access to services an attacker must connect to the service to successful carry out the exploit. Reducing the number of systems that are allowed to connect to the service will prevent an attack from working when launched outside an allowed ranges. 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{"configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "13C802F5-27EF-43DE-AD8A-2AEAB52A9CCB", "versionEndIncluding": "5.15.0-58", "versionStartIncluding": "4.4.0-96.119", "vulnerable": true}], "negate": false, "operator": "OR"}]}, {"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*", "matchCriteriaId": "F4CFF558-3C47-480D-A2F0-BABF26042943", "vulnerable": true}, {"criteria": "cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:*", "matchCriteriaId": "7F6FB57C-2BC7-487C-96DD-132683AEB35D", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "A flaw was found in the Linux kernel's memory deduplication mechanism. The max page sharing of Kernel Samepage Merging (KSM), added in Linux kernel version 4.4.0-96.119, can create a side channel. When the attacker and the victim share the same host and the default setting of KSM is \"max page sharing=256\", it is possible for the attacker to time the unmap to merge with the victim's page. The unmapping time depends on whether it merges with the victim's page and additional physical pages are created beyond the KSM's \"max page share\". Through these operations, the attacker can leak the victim's page."}, {"lang": "es", "value": "Se encontr\u00f3 un fallo en el mecanismo de deduplicaci\u00f3n de memoria del kernel de Linux. El uso compartido m\u00e1ximo de p\u00e1ginas de Kernel Samepage Merging (KSM), agregado en la versi\u00f3n 4.4.0-96.119 del kernel de Linux, puede crear un canal lateral. Cuando el atacante y la v\u00edctima comparten el mismo host y la configuraci\u00f3n predeterminada de KSM es \"max page sharing=256\", es posible que el atacante programe la desasignaci\u00f3n para fusionarse con la p\u00e1gina de la v\u00edctima. El tiempo de desasignaci\u00f3n depende de si se fusiona con la p\u00e1gina de la v\u00edctima y si se crean p\u00e1ginas f\u00edsicas adicionales m\u00e1s all\u00e1 del \"max page share\" de KSM. Mediante estas operaciones, el atacante puede filtrar la p\u00e1gina de la v\u00edctima."}], "id": "CVE-2024-0564", "lastModified": "2024-02-08T16:36:48.837", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "ADJACENT_NETWORK", "availabilityImpact": "NONE", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}, {"cvssData": {"attackComplexity": "HIGH", "attackVector": "ADJACENT_NETWORK", "availabilityImpact": "NONE", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 1.6, "impactScore": 3.6, "source": "secalert@redhat.com", "type": "Secondary"}]}, "published": "2024-01-30T15:15:08.687", "references": [{"source": "secalert@redhat.com", "tags": ["Third Party Advisory"], "url": "https://access.redhat.com/security/cve/CVE-2024-0564"}, {"source": "secalert@redhat.com", "tags": ["Exploit", "Issue Tracking"], "url": "https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1680513"}, {"source": "secalert@redhat.com", "tags": ["Issue Tracking"], "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2258514"}, {"source": "secalert@redhat.com", "tags": ["Not Applicable"], "url": "https://link.springer.com/conference/wisa"}, {"source": "secalert@redhat.com", "tags": ["Not Applicable"], "url": "https://wisa.or.kr/accepted"}], "sourceIdentifier": "secalert@redhat.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-203"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: max page sharing of Kernel Samepage Merging (KSM) may cause memory deduplication", "id": "2258514", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2258514"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.3", "cvss3_scoring_vector": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N", "status": "draft"}, "details": ["A flaw was found in the Linux kernel's memory deduplication mechanism. The max page sharing of Kernel Samepage Merging (KSM), added in Linux kernel version 4.4.0-96.119, can create a side channel. When the attacker and the victim share the same host and the default setting of KSM is \"max page sharing=256\", it is possible for the attacker to time the unmap to merge with the victim's page. The unmapping time depends on whether it merges with the victim's page and additional physical pages are created beyond the KSM's \"max page share\". Through these operations, the attacker can leak the victim's page.", "A flaw was found in the Linux kernel's memory deduplication mechanism. The max page sharing of Kernel Samepage Merging (KSM), added in Linux kernel version 4.4.0-96.119, can create a side channel. When the attacker and the victim share the same host and the default setting of KSM is \"max page sharing=256\", it is possible for the attacker to time the unmap to merge with the victim's page. The unmapping time depends on whether it merges with the victim's page and additional physical pages are created beyond the KSM's \"max page share\". Through these operations, the attacker can leak the victim's page."], "mitigation": {"lang": "en:us", "value": "The mitigation shown below has a potentially significant impact on system performance and stability. It should be carefully tested prior to deployment:\n- Deactivation of memory deduplication \nDeactivating memory deduplication will effectively mitigate all attack vectors. This measure unfortunately eliminates all the highly appreciated benefits of memory deduplication, namely the increase of operational cost-effectiveness through inter-VM memory sharing. This will cause an increase in the amount of memory required and in some situations may adversely impact performance (e.g. due to slower swap space being used). It is recommended that customers test this workaround before using it in production. See https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/virtualization_tuning_and_optimization_guide/sect-ksm-deactivating_ksm for how to disable KSM from Red Hat Enterprise Linux 6 and newer.\n- Disabling services and firewall rules.\nThe attack uses the response time of services on the system. By limiting access to services an attacker must connect to the service to successful carry out the exploit. Reducing the number of systems that are allowed to connect to the service will prevent an attack from working when launched outside an allowed ranges. While this does not prevent an attack from working, it will reduce the amount of systems that an attacker can launch an attack from."}, "name": "CVE-2024-0564", "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": "Will not fix", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Will not fix", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Will not fix", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Will not fix", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2024-01-20T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2024-0564\nhttps://nvd.nist.gov/vuln/detail/CVE-2024-0564\nhttps://bugs.launchpad.net/ubuntu/+source/linux/+bug/1680513\nhttps://link.springer.com/conference/wisa\nhttps://wisa.or.kr/accepted"], "statement": "This issue affects the Linux Kernel versions included with Red Hat Enterprise Linux 7, 8, and 9. Red Hat Product Security has rated the security impact of this issue as low. Additionally, a workaround is available, and a future update may address this issue.\nTo exploit this vulnerability, both the attacker and the victim must be on the same host, with the 'max page sharing' parameter set to 256. The attacker cannot influence the victim to write to the same pages that can be 'unmapped' to read unauthorized data. Due to the complexity of timing and the requirement for the attacker to have a local account, this vulnerability is very difficult to exploit, resulting in a low impact rating.\nFor additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.", "threat_severity": "Low"}