{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-81666", "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749", "state": "PUBLISHED", "assignerShortName": "redhat", "dateReserved": "2026-08-27T10:38:28.793Z", "datePublished": "2026-09-04T09:46:06.130Z", "dateUpdated": "2026-09-04T09:46:06.130Z"}, "containers": {"cna": {"title": "Corosync: corosync: integer overflow in check_memb_commit_token_sanity may bypass message length validation on 32-bit systems", "metrics": [{"other": {"content": {"value": "Moderate", "namespace": "https://access.redhat.com/security/updates/classification/"}, "type": "Red Hat severity rating"}}, {"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "ADJACENT_NETWORK", "availabilityImpact": "HIGH", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "format": "CVSS"}], "descriptions": [{"lang": "en", "value": "An integer overflow was found in Corosync's handling of membership commit token messages. The length-validation check for these messages can be bypassed on 32-bit systems due to an integer overflow in the calculation of the expected message length, allowing a crafted network packet to trigger an out-of-bounds memory access that crashes the Corosync daemon. This results in a denial of service for the affected cluster node. The overflow does not occur on 64-bit systems, where the length calculation is correctly performed in 64-bit arithmetic."}], "affected": [{"vendor": "Red Hat", "product": "Red Hat Enterprise Linux 10", "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "packageName": "corosync", "defaultStatus": "affected", "cpes": ["cpe:/o:redhat:enterprise_linux:10"]}, {"vendor": "Red Hat", "product": "Red Hat Enterprise Linux 7", "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "packageName": "corosync", "defaultStatus": "affected", "cpes": ["cpe:/o:redhat:enterprise_linux:7"]}, {"vendor": "Red Hat", "product": "Red Hat Enterprise Linux 8", "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "packageName": "corosync", "defaultStatus": "affected", "cpes": ["cpe:/o:redhat:enterprise_linux:8"]}, {"vendor": "Red Hat", "product": "Red Hat Enterprise Linux 9", "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "packageName": "corosync", "defaultStatus": "affected", "cpes": ["cpe:/o:redhat:enterprise_linux:9"]}, {"vendor": "Red Hat", "product": "Red Hat OpenShift Container Platform 4", "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "packageName": "rhcos", "defaultStatus": "affected", "cpes": ["cpe:/a:redhat:openshift:4"]}], "references": [{"url": "https://access.redhat.com/security/cve/CVE-2026-81666", "tags": ["vdb-entry", "x_refsource_REDHAT"]}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2524923", "name": "RHBZ#2524923", "tags": ["issue-tracking", "x_refsource_REDHAT"]}], "datePublic": "2026-09-04T08:14:29.525Z", "problemTypes": [{"descriptions": [{"cweId": "CWE-190", "description": "Integer Overflow or Wraparound", "lang": "en", "type": "CWE"}]}], "x_redhatCweChain": "CWE-190: Integer Overflow or Wraparound", "workarounds": [{"lang": "en", "value": "There is no complete mitigation for this vulnerability short of a fix, but the following steps reduce risk:\n\n1. Ensure cluster message authentication is enabled in corosync.conf (crypto_cipher=aes256, crypto_hash=sha256 with a shared key from corosync-keygen), which is the default when clusters are configured via 'pcs cluster setup', and disabling it (cipher=none/hash=none) is an explicitly unsupported configuration per upstream maintainer guidance.\n2. Restrict network access to the cluster communication ports (default 5405-5412/UDP) to trusted cluster node addresses only.\n3. Where architecturally feasible, prefer 64-bit deployments, since the integer overflow described here does not occur on 64-bit systems."}], "timeline": [{"lang": "en", "time": "2026-08-23T00:00:00.000Z", "value": "Reported to Red Hat."}, {"lang": "en", "time": "2026-09-04T08:14:29.525Z", "value": "Made public."}], "credits": [{"lang": "en", "value": "Red Hat would like to thank Tristan Madani (Talence Security) for reporting this issue."}], "providerMetadata": {"orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749", "shortName": "redhat", "dateUpdated": "2026-09-04T09:46:06.130Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}}}

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{"affected": [{"affectedData": [{"collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": ["cpe:/o:redhat:enterprise_linux:10"], "defaultStatus": "affected", "packageName": "corosync", "product": "Red Hat Enterprise Linux 10", "vendor": "Red Hat"}, {"collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": ["cpe:/o:redhat:enterprise_linux:7"], "defaultStatus": "affected", "packageName": "corosync", "product": "Red Hat Enterprise Linux 7", "vendor": "Red Hat"}, {"collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": ["cpe:/o:redhat:enterprise_linux:8"], "defaultStatus": "affected", "packageName": "corosync", "product": "Red Hat Enterprise Linux 8", "vendor": "Red Hat"}, {"collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": ["cpe:/o:redhat:enterprise_linux:9"], "defaultStatus": "affected", "packageName": "corosync", "product": "Red Hat Enterprise Linux 9", "vendor": "Red Hat"}, {"collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": ["cpe:/a:redhat:openshift:4"], "defaultStatus": "affected", "packageName": "rhcos", "product": "Red Hat OpenShift Container Platform 4", "vendor": "Red Hat"}], "source": "[email protected]"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "An integer overflow was found in Corosync's handling of membership commit token messages. The length-validation check for these messages can be bypassed on 32-bit systems due to an integer overflow in the calculation of the expected message length, allowing a crafted network packet to trigger an out-of-bounds memory access that crashes the Corosync daemon. This results in a denial of service for the affected cluster node. The overflow does not occur on 64-bit systems, where the length calculation is correctly performed in 64-bit arithmetic."}], "id": "CVE-2026-81666", "lastModified": "2026-09-04T10:17:13.187", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "ADJACENT_NETWORK", "availabilityImpact": "HIGH", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 3.6, "source": "[email protected]", "type": "Primary"}]}, "published": "2026-09-04T10:17:13.187", "references": [{"source": "[email protected]", "url": "https://access.redhat.com/security/cve/CVE-2026-81666"}, {"source": "[email protected]", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2524923"}], "sourceIdentifier": "[email protected]", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-190"}], "source": "[email protected]", "type": "Primary"}]}

{"acknowledgement": "Red Hat would like to thank Tristan Madani (Talence Security) for reporting this issue.", "bugzilla": {"description": "corosync: corosync: integer overflow in check_memb_commit_token_sanity may bypass message length validation on 32-bit systems", "id": "2524923", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2524923"}, "csaw": false, "cvss3": {"cvss3_base_score": "6.5", "cvss3_scoring_vector": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-190", "details": ["An integer overflow was found in Corosync's handling of membership commit token messages. The length-validation check for these messages can be bypassed on 32-bit systems due to an integer overflow in the calculation of the expected message length, allowing a crafted network packet to trigger an out-of-bounds memory access that crashes the Corosync daemon. This results in a denial of service for the affected cluster node. The overflow does not occur on 64-bit systems, where the length calculation is correctly performed in 64-bit arithmetic."], "mitigation": {"lang": "en:us", "value": "There is no complete mitigation for this vulnerability short of a fix, but the following steps reduce risk:\n1. Ensure cluster message authentication is enabled in corosync.conf (crypto_cipher=aes256, crypto_hash=sha256 with a shared key from corosync-keygen), which is the default when clusters are configured via 'pcs cluster setup', and disabling it (cipher=none/hash=none) is an explicitly unsupported configuration per upstream maintainer guidance.\n2. Restrict network access to the cluster communication ports (default 5405-5412/UDP) to trusted cluster node addresses only.\n3. Where architecturally feasible, prefer 64-bit deployments, since the integer overflow described here does not occur on 64-bit systems."}, "name": "CVE-2026-81666", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "corosync", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Fix deferred", "package_name": "corosync", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "corosync", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "corosync", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "rhcos", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-09-04T08:14:29Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-81666\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-81666"], "statement": "This vulnerability is rated as Moderate. The published Red Hat CVSS score is 6.5 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), matching the unmitigated upstream baseline for 32-bit deployments.\nThe integer overflow described only affects 32-bit builds, because C integer-promotion rules cause the vulnerable multiplication to be evaluated in 64-bit arithmetic on 64-bit systems, which prevents the overflow entirely. Red Hat Enterprise Linux 8, 9, and 10 ship primarily 64-bit architectures (x86_64, aarch64), so this specific overflow mechanism does not apply to the vast majority of Red Hat deployments; this remains true regardless of the encryption scoring decision below.\nAs with the related totempg heap overflow (see CVE-2026-81665), RHEL High Availability Add-On clusters configured via 'pcs cluster setup' default to cluster message authentication enabled (crypto_hash=sha256, crypto_cipher=aes256), which meaningfully reduces real-world risk. This has been confirmed directly with upstream corosync maintainer Jan Friesse (2026-08-31), who also confirmed this protection is a configurable default rather than an enforced control for RHEL <=10: an administrator can disable it via the officially supported 'pcs' interface (cipher=none, hash=none), not just by unsupported manual editing. Because this protection can be turned off through a supported configuration path, Red Hat is publishing the CVSS score for the worst-case supported configuration (encryption disabled) rather than crediting the default as a permanent mitigating factor.\nAdministrators who have not explicitly disabled cluster message authentication benefit from a reduced practical risk, equivalent to CVSS 4.5 (CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H). See the Mitigation section for guidance on confirming and enforcing this configuration.\nCorosync is shipped in Red Hat Enterprise Linux 7 through 10 and RHIVOS as part of the High Availability Add-On.\nNote: upstream corosync HEAD and current Fedora (which will become RHEL 11) now enforce encryption at compile time, removing the ability to disable it entirely without recompiling from source. Once this reaches RHEL as a supported release, this compensating control will become a true enforced guarantee rather than a configurable default, and the published score is expected to be revisited at that time.", "threat_severity": "Moderate"}

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