Temporal Server up to 0.x/1.29.7/1.30.6/1.31.2 Pagination Token workflowHandler.go improper authorization

Summaryinfo

A vulnerability labeled as problematic has been found in Temporal Server up to 0.x/1.29.7/1.30.6/1.31.2. Affected is an unknown function of the file service/frontend/workflowHandler.go of the component Pagination Token. Executing a manipulation can lead to improper authorization. This vulnerability is handled as CVE-2026-87857. The attack can be executed remotely. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Temporal Server up to 0.x/1.29.7/1.30.6/1.31.2. It has been declared as problematic. This vulnerability affects an unknown part of the file service/frontend/workflowHandler.go of the component Pagination Token. The manipulation with an unknown input leads to a improper authorization vulnerability. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect confidentiality. CVE summarizes:

Temporal Server does not bind a workflow-history pagination token to the namespace and workflow named in the request that presents it. GetWorkflowExecutionHistory and GetWorkflowExecutionHistoryReverse authorize the caller against the namespace in the request, then select history from the branch recorded inside the caller-supplied next_page_token. The normal history continuation carries a run identifier, event bounds, a persistence cursor, and a branch token, but no namespace or workflow identity, and it is serialized as unauthenticated protobuf bytes. An authenticated caller holding read permission on one namespace, together with a genuine non-final continuation issued earlier for a workflow in a second namespace, can submit that continuation with a request naming the first namespace and receive the second namespace's workflow history, provided the supplied workflow identifier selects the same History shard as the continuation's branch. No workflow with the supplied identifier needs to exist. Because the token is unauthenticated, a holder can also advance its event range and clear its persistence cursor, which returns history events created after that caller's current credential no longer granted access to the continuation's namespace. Determining exposure is a version question rather than a configuration question: every release listed as affected omits the binding check on the forward history path, and on the reverse history path in releases from 1.16.0, which introduced GetWorkflowExecutionHistoryReverse; no setting in an affected release restores it, and affected releases emit no metric or log for the condition, so their telemetry provides no detection. Fixed releases add the check and, when a page token's branch token is not the requested execution's current branch token, record the counter pagination_token_branch_mismatch tagged with namespace and reason and write a History-service warning log reading "Pagination branch token is not the execution's current branch token" with the fields wf-namespace, wf-id, wf-run-id, reason, wf-branch-token, and wf-request-branch-token. Search History warning logs for that message, or for reason=foreign_branch, which denotes a branch token the requested execution never recorded and is not expected in normal operation; reason=non_current_branch denotes a retained but superseded branch of the same execution and can occur legitimately after conflict resolution or failover. A foreign_branch record does not by itself prove the read was refused, because the counter and log are emitted before the enforcement decision and therefore appear both when the check rejects the request and when history.enablePaginationTokenBranchValidationShadowMode is enabled and the read is served; confirm refusal from the gRPC response, which is InvalidArgument carrying a CurrentBranchChangedFailure detail. The metric and log are tagged with the requesting namespace, not the namespace whose history the token selects, so a foreign_branch alert does not name the exposed namespace. The issue does not provide unauthenticated access, construction of a usable continuation from public workflow identifiers, enumeration of workflows for which the caller holds no continuation, or any modification of workflow state.

The advisory is available at github.com. This vulnerability was named CVE-2026-87857 since 09/09/2026. The exploitation appears to be easy. The attack can be initiated remotely. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1548.002 by the MITRE ATT&CK project.

Upgrading to version 1.0.0, 1.30.7 or 1.31.3 eliminates this vulnerability.

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Productinfo

Vendor

• Temporal

Name

• Server

Version

• 0.x
• 1.29.0
• 1.29.1
• 1.29.2
• 1.29.3
• 1.29.4
• 1.29.5
• 1.29.6
• 1.29.7
• 1.30.0
• 1.30.1
• 1.30.2
• 1.30.3
• 1.30.4
• 1.30.5
• 1.30.6
• 1.31.0
• 1.31.1
• 1.31.2

CPE 2.3info

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CPE 2.2info

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