CVE-2026-39944

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{"affected": [{"affectedData": [{"product": "ceph", "vendor": "ceph", "versions": [{"status": "affected", "version": ">= 19.0.0, < 19.2.6"}, {"status": "affected", "version": ">= 20.0.0, < 20.2.4"}]}], "source": "security-advisories@github.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Ceph is an open-source distributed storage platform providing object, block, and file storage. In versions prior to 20.2.4 and 19.2.6, the RADOS Gateway (RGW) protects STS session tokens with an AES-128-CBC handler that provides no message authentication, allowing an attacker who holds any valid STS token to tamper with it undetected and escalate to full RGW administrative access. Because the ciphertext is unauthenticated, the attacker can perform a CBC bit-flip on the acct_type, perm_type, and is_admin fields of their own token, and a forged is_admin value triggers a global administrative override that bypasses all capability checks. The attack is reachable remotely over the RGW S3 endpoint and is a self-contained modification of a token the attacker already possesses, requiring no encryption oracle and no network observation. It requires only a single valid STS token, which need not carry any elevated privileges, with STS enabled. This issue is fixed in versions 20.2.4 and 19.2.6."}], "id": "CVE-2026-39944", "lastModified": "2026-09-08T21:11:56.250", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 8.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 5.9, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-39944", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-08-31T00:00:00+00:00", "version": "2.0.3"}}]}, "published": "2026-08-28T00:17:27.860", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/ceph/ceph/releases/tag/v19.2.6"}, {"source": "security-advisories@github.com", "url": "https://github.com/ceph/ceph/releases/tag/v20.2.4"}, {"source": "security-advisories@github.com", "url": "https://github.com/ceph/ceph/security/advisories/GHSA-j73r-qrgx-jvq2"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Awaiting Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-327"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{"bugzilla": {"description": "ceph: ceph: RGW STS session tokens vulnerable to CBC bit-flip attack enabling admin privilege escalation", "id": "2519431", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2519431"}, "csaw": false, "cvss3": {"cvss3_base_score": "8.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-327", "details": ["A flaw was found in Ceph RGW's STS (Security Token Service) session token implementation. The STS tokens use the same unauthenticated AES-128-CBC encryption as CephX, which lacks message authentication and uses a hardcoded initialization vector. Because there is no integrity protection on the tokens, an attacker who holds any valid unprivileged STS token can perform a CBC bit-flip attack to modify the token contents and escalate to full RGW admin privileges. This requires only that STS is enabled (rgw_s3_auth_use_sts = true) and that the attacker has a single valid STS token. Successful exploitation grants complete control over the RGW service, including reading, writing, and deleting all objects and buckets."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability."}, "name": "CVE-2026-39944", "package_state": [{"cpe": "cpe:/a:redhat:ceph_storage:4", "fix_state": "Fix deferred", "package_name": "ceph", "product_name": "Red Hat Ceph Storage 4"}, {"cpe": "cpe:/a:redhat:ceph_storage:5", "fix_state": "Fix deferred", "package_name": "ceph", "product_name": "Red Hat Ceph Storage 5"}, {"cpe": "cpe:/a:redhat:ceph_storage:6", "fix_state": "Fix deferred", "package_name": "ceph", "product_name": "Red Hat Ceph Storage 6"}, {"cpe": "cpe:/a:redhat:ceph_storage:7", "fix_state": "Fix deferred", "package_name": "ceph", "product_name": "Red Hat Ceph Storage 7"}, {"cpe": "cpe:/a:redhat:ceph_storage:7", "fix_state": "Fix deferred", "package_name": "rhceph/rhceph-7-rhel9", "product_name": "Red Hat Ceph Storage 7"}, {"cpe": "cpe:/a:redhat:ceph_storage:8", "fix_state": "Fix deferred", "package_name": "ceph", "product_name": "Red Hat Ceph Storage 8"}, {"cpe": "cpe:/a:redhat:ceph_storage:8", "fix_state": "Fix deferred", "package_name": "rhceph/rhceph-8-rhel9", "product_name": "Red Hat Ceph Storage 8"}, {"cpe": "cpe:/a:redhat:ceph_storage:9", "fix_state": "Fix deferred", "package_name": "ceph", "product_name": "Red Hat Ceph Storage 9"}, {"cpe": "cpe:/a:redhat:ceph_storage:9", "fix_state": "Fix deferred", "package_name": "rhceph/rhceph-9-rhel9", "product_name": "Red Hat Ceph Storage 9"}], "public_date": "2026-08-19T17:57:46Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-39944\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-39944"], "statement": "The Red Hat Product Security team has assessed the severity of this vulnerability as Important, given that it can be exploited over the network by any holder of a valid STS token without user interaction. Successful exploitation allows an attacker to escalate from any unprivileged STS session to full RGW admin, gaining complete read, write, and delete access to all S3 objects and buckets. The vulnerability's root cause is the use of unauthenticated AES-128-CBC encryption in STS session tokens, sharing the same cryptographic weakness as CVE-2025-30156.", "threat_severity": "Important"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": null}], "enrichment": {"confidence": 100.0, "confidence_source": "manual", "scores": [{"score": 100.0, "source": "manual"}]}, "product": "ceph", "vendor": "ceph"}], "created": "2026-08-20T08:45:12.396291+00:00", "updated": "2026-08-28T06:30:18.394237+00:00", "vendors": ["ceph", "ceph$PRODUCT$ceph"]}