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CVE-2026-87858

Estado: Pendiente de análisisAlta (7.2)—

Temporal Server decided whether a Workflow completion callback was internal by reading a caller-supplied HTTP header. An authenticated caller holding only write permission in a single namespace could attach a completion callback whose URL host matched the configured callback address allowlist, whose URL path was any Temporal HTTP API route, and whose header map contained a non-empty header named source.

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When the History service delivered that callback, the non-empty source header caused it to re-target the request at the local frontend client and rewrite only the scheme and host, preserving the caller's path, query, and request body. Where an internal frontend is deployed with its HTTP API enabled, that client resolves to the internal frontend, which authorizes every request as a system administrator without requiring authentication information. The result is that the server performs an attacker-chosen state-changing HTTP POST against its own administrative API on the caller's behalf, in namespaces where the caller has no permission. The caller never needs network access to the internal frontend, because the History service makes the request. Confirmed effects include terminating Workflows in other namespaces, registering namespaces, modifying another namespace's configuration, and deleting another namespace and its Workflows. The affected routing logic is present in both the HSM and CHASM callback delivery implementations. This description and the CVSS score in this record describe releases 1.30.0 and later, where any non-empty source header is sufficient. Releases 1.25.0 through 1.29.7 are affected by a narrower form of the same defect in which the header must exactly match a configured cluster ID, a UUID that a namespace-scoped caller cannot read through the API. The consequence once that match occurs is the same, but the attack is materially harder and scores lower. To determine whether a deployment is affected, check two settings together: the static Server configuration for a non-zero services.internal-frontend.rpc.httpPort, and the effective per-namespace dynamic configuration value of component.callbacks.allowedAddresses. A deployment is exposed only when an internal frontend is deployed with a non-zero HTTP port, at least one allowlist rule admits a host, and authorization is enabled. The allowlist is empty by default, which denies all external callback URLs, and the stock static topology does not include an internal frontend. Note that a failed attach returns the error 'invalid url: url does not match any configured callback address', which proves only that one tested URL did not match and does not prove the effective allowlist is empty. To look for callbacks already attached, use DescribeWorkflowExecution, which returns callback information for a Workflow's registered completion callbacks. Operators should be aware of a gap when searching for evidence of delivery: the frontend HTTP API server records the request method and URL at debug level only, so at default log levels a delivered request is not written to the internal frontend's logs, and the absence of such log entries is not evidence that the issue was not exploited.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Atacante autenticado explota CWE-807 (validación de headers) en Temporal Server para realizar solicitudes HTTP POST administrativas sin autenticación contra la API interna, logrando acceso como administrador del sistema y manipulación de configuración y workflows.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Privileged Account ManagementVulnerability ScanningUser TrainingUser Account ManagementThreat Intelligence ProgramRestrict File and Directory Permissions

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Temporal — Temporal ServerAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-87858",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-87858",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-09-21T15:25:09.392404Z"
        }
      }
    ],
    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "security@temporal.io",
        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
          "Recovery": "NOT_DEFINED",
          "baseScore": 7.2,
          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "exploitMaturity": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "privilegesRequired": "LOW",
          "subIntegrityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "vulnAvailabilityImpact": "HIGH",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "subConfidentialityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "confidentialityRequirement": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
        }
      }
    ]
  },
  "affected": [
    {
      "source": "security@temporal.io",
      "affectedData": [
        {
          "cpes": [
            "cpe:2.3:a:temporal:temporal:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/temporalio/temporal",
          "vendor": "Temporal Technologies, Inc.",
          "modules": [
            "History",
            "Frontend"
          ],
          "product": "Temporal Server",
          "versions": [
            {
              "status": "affected",
              "version": "1.30.0",
              "lessThan": "1.30.7",
              "versionType": "semver"
            },
            {
              "status": "affected",
              "version": "1.31.0",
              "lessThan": "1.31.3",
              "versionType": "semver"
            }
          ],
          "packageName": "go.temporal.io/server",
          "programFiles": [
            "components/callbacks/request.go",
            "chasm/lib/callback/request.go",
            "service/frontend/workflow_handler.go",
            "common/authorization/claim_mapper.go"
          ],
          "collectionURL": "https://pkg.go.dev",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "routeRequest"
            },
            {
              "name": "validateWorkflowCompletionCallbacks"
            },
            {
              "name": "validateCallbackURL"
            },
            {
              "name": "internalClaimMapper.GetClaims"
            }
          ]
        },
        {
          "cpes": [
            "cpe:2.3:a:temporal:temporal:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/temporalio/temporal",
          "vendor": "Temporal Technologies, Inc.",
          "modules": [
            "History",
            "Frontend"
          ],
          "product": "Temporal Server",
          "versions": [
            {
              "status": "affected",
              "version": "1.25.0",
              "versionType": "semver",
              "lessThanOrEqual": "1.29.7"
            }
          ],
          "packageName": "go.temporal.io/server",
          "programFiles": [
            "components/callbacks/fx.go",
            "service/frontend/workflow_handler.go",
            "common/authorization/claim_mapper.go"
          ],
          "collectionURL": "https://pkg.go.dev",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "HTTPCallerProviderProvider"
            },
            {
              "name": "validateWorkflowCompletionCallbacks"
            },
            {
              "name": "validateCallbackURL"
            },
            {
              "name": "internalClaimMapper.GetClaims"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-09-21T12:17:22.230",
  "references": [
    {
      "url": "https://github.com/temporalio/temporal/pull/11965",
      "source": "security@temporal.io"
    },
    {
      "url": "https://github.com/temporalio/temporal/pull/11982",
      "source": "security@temporal.io"
    },
    {
      "url": "https://github.com/temporalio/temporal/pull/12085",
      "source": "security@temporal.io"
    },
    {
      "url": "https://github.com/temporalio/temporal/releases/tag/v1.30.7",
      "source": "security@temporal.io"
    },
    {
      "url": "https://github.com/temporalio/temporal/releases/tag/v1.31.3",
      "source": "security@temporal.io"
    },
    {
      "url": "https://github.com/temporalio/temporal/releases/tag/v1.32.0",
      "source": "security@temporal.io"
    }
  ],
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security@temporal.io",
      "description": [
        {
          "lang": "en",
          "value": "CWE-807"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Temporal Server decided whether a Workflow completion callback was internal by reading a caller-supplied HTTP header. An authenticated caller holding only write permission in a single namespace could attach a completion callback whose URL host matched the configured callback address allowlist, whose URL path was any Temporal HTTP API route, and whose header map contained a non-empty header named source. When the History service delivered that callback, the non-empty source header caused it to re-target the request at the local frontend client and rewrite only the scheme and host, preserving the caller's path, query, and request body. Where an internal frontend is deployed with its HTTP API enabled, that client resolves to the internal frontend, which authorizes every request as a system administrator without requiring authentication information. The result is that the server performs an attacker-chosen state-changing HTTP POST against its own administrative API on the caller's behalf, in namespaces where the caller has no permission. The caller never needs network access to the internal frontend, because the History service makes the request. Confirmed effects include terminating Workflows in other namespaces, registering namespaces, modifying another namespace's configuration, and deleting another namespace and its Workflows. The affected routing logic is present in both the HSM and CHASM callback delivery implementations. This description and the CVSS score in this record describe releases 1.30.0 and later, where any non-empty source header is sufficient. Releases 1.25.0 through 1.29.7 are affected by a narrower form of the same defect in which the header must exactly match a configured cluster ID, a UUID that a namespace-scoped caller cannot read through the API. The consequence once that match occurs is the same, but the attack is materially harder and scores lower. To determine whether a deployment is affected, check two settings together: the static Server configuration for a non-zero services.internal-frontend.rpc.httpPort, and the effective per-namespace dynamic configuration value of component.callbacks.allowedAddresses. A deployment is exposed only when an internal frontend is deployed with a non-zero HTTP port, at least one allowlist rule admits a host, and authorization is enabled. The allowlist is empty by default, which denies all external callback URLs, and the stock static topology does not include an internal frontend. Note that a failed attach returns the error 'invalid url: url does not match any configured callback address', which proves only that one tested URL did not match and does not prove the effective allowlist is empty. To look for callbacks already attached, use DescribeWorkflowExecution, which returns callback information for a Workflow's registered completion callbacks. Operators should be aware of a gap when searching for evidence of delivery: the frontend HTTP API server records the request method and URL at debug level only, so at default log levels a delivered request is not written to the internal frontend's logs, and the absence of such log entries is not evidence that the issue was not exploited."
    }
  ],
  "lastModified": "2026-09-22T19:40:05.870",
  "sourceIdentifier": "security@temporal.io"
}