CVE-2026-39944 (GCVE-0-2026-39944)

Vulnerability from cvelistv5 – Published: 2026-08-27 20:47 – Updated: 2026-08-28 15:57
VLAI
Title
Ceph: CephX AES Authentication error
Summary
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.
Severity
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-28 15:45 UTC
CWE
  • CWE-327 - Use of a Broken or Risky Cryptographic Algorithm
Assigner
References
Impacted products
Vendor Product Version CPE status
ceph ceph Affected: >= 19.0.0, < 19.2.6
Affected: >= 20.0.0, < 20.2.4
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-39944",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-28T15:45:42.373340Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-28T15:57:39.530Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "ceph",
          "vendor": "ceph",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 19.0.0, \u003c 19.2.6"
            },
            {
              "status": "affected",
              "version": "\u003e= 20.0.0, \u003c 20.2.4"
            }
          ]
        }
      ],
      "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "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"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-327",
              "description": "CWE-327: Use of a Broken or Risky Cryptographic Algorithm",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-27T20:47:01.512Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/ceph/ceph/security/advisories/GHSA-j73r-qrgx-jvq2",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/ceph/ceph/security/advisories/GHSA-j73r-qrgx-jvq2"
        },
        {
          "name": "https://github.com/ceph/ceph/releases/tag/v19.2.6",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/ceph/ceph/releases/tag/v19.2.6"
        },
        {
          "name": "https://github.com/ceph/ceph/releases/tag/v20.2.4",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/ceph/ceph/releases/tag/v20.2.4"
        }
      ],
      "source": {
        "advisory": "GHSA-j73r-qrgx-jvq2",
        "discovery": "UNKNOWN"
      },
      "title": "Ceph: CephX AES Authentication error"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-39944",
    "datePublished": "2026-08-27T20:47:01.512Z",
    "dateReserved": "2026-04-07T22:40:33.820Z",
    "dateUpdated": "2026-08-28T15:57:39.530Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-39944",
      "date": "2026-08-28",
      "epss": "0.0017",
      "percentile": "0.06572"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-39944\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-08-28T00:17:27.860\",\"lastModified\":\"2026-08-28T20:17:28.780\",\"vulnStatus\":\"Received\",\"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.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"ceph\",\"product\":\"ceph\",\"versions\":[{\"version\":\"\u003e= 19.0.0, \u003c 19.2.6\",\"status\":\"affected\"},{\"version\":\"\u003e= 20.0.0, \u003c 20.2.4\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":8.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.8,\"impactScore\":5.9}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-08-28T15:45:42.373340Z\",\"id\":\"CVE-2026-39944\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"total\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-327\"}]}],\"references\":[{\"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\",\"source\":\"security-advisories@github.com\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-08-27T23:37:34+00:00",
      "cve": "CVE-2026-39944",
      "id": "CVE-2026-39944",
      "initial_release_date": "2026-08-19T17:57:46+00:00",
      "product_status:known_affected": "195",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "ceph: ceph: RGW STS session tokens vulnerable to CBC bit-flip attack enabling admin privilege escalation",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39944.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-39944\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-08-28T15:45:42.373340Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-08-28T15:45:43.387Z\"}}], \"cna\": {\"title\": \"Ceph: CephX AES Authentication error\", \"source\": {\"advisory\": \"GHSA-j73r-qrgx-jvq2\", \"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 8.8, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"LOW\", \"confidentialityImpact\": \"HIGH\"}}], \"affected\": [{\"vendor\": \"ceph\", \"product\": \"ceph\", \"versions\": [{\"status\": \"affected\", \"version\": \"\u003e= 19.0.0, \u003c 19.2.6\"}, {\"status\": \"affected\", \"version\": \"\u003e= 20.0.0, \u003c 20.2.4\"}]}], \"references\": [{\"url\": \"https://github.com/ceph/ceph/security/advisories/GHSA-j73r-qrgx-jvq2\", \"name\": \"https://github.com/ceph/ceph/security/advisories/GHSA-j73r-qrgx-jvq2\", \"tags\": [\"x_refsource_CONFIRM\"]}, {\"url\": \"https://github.com/ceph/ceph/releases/tag/v19.2.6\", \"name\": \"https://github.com/ceph/ceph/releases/tag/v19.2.6\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://github.com/ceph/ceph/releases/tag/v20.2.4\", \"name\": \"https://github.com/ceph/ceph/releases/tag/v20.2.4\", \"tags\": [\"x_refsource_MISC\"]}], \"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.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-327\", \"description\": \"CWE-327: Use of a Broken or Risky Cryptographic Algorithm\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2026-08-27T20:47:01.512Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-39944\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-28T15:57:39.530Z\", \"dateReserved\": \"2026-04-07T22:40:33.820Z\", \"assignerOrgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"datePublished\": \"2026-08-27T20:47:01.512Z\", \"assignerShortName\": \"GitHub_M\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.