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CVE-2026-87857— Temporal Server workflow-history pagination token is not bound to the requested namespace and workflow

Quick assessment

Affected
Temporal Technologies, Inc. Temporal Server
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Temporal Server 未将工作流历史分页令牌（pagination token）绑定到请求中所指定的命名空间（namespace）和工作流名称。 和 接口首先根据请求中的命名空间对调用者进行授权，随后从调用者提供的 中记录的分支（branch）选取历史数据。常规的历史延续（continuation）包含运行标识符（run identifier）、事件边界（event bounds）、持久化游标（persistence cursor）和分支令牌（branch token），但不包含命名空间或工作流身份标识；

CVSS 5.3 · Medium

Affected Version Matrix 4

VendorProduct Version RangeStatus
Temporal Technologies, Inc. Temporal Server 0.0.0< 1.0.0 unknown
1.0.0≤ 1.29.7 affected
1.30.0< 1.30.7 affected
1.31.0< 1.31.3 affected
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I. Basic Information for CVE-2026-87857

Vulnerability Information
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Vulnerability Title
Temporal Server workflow-history pagination token is not bound to the requested namespace and workflow
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Temporal Technologies, Inc. Temporal Server 1.0.0 ~ 1.29.7 cpe:2.3:a:temporal:temporal:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-87857

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III. Intelligence Information for CVE-2026-87857

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Other References for CVE-2026-87857 (3)

Other References for CVE-2026-87857 (9)

IV. Related Vulnerabilities

Same product: Temporal Server
Same vendor: Temporal Technologies, Inc.
Same weakness: CWE-639