VulnerabilityPublished 9 Nov 2026

CVE-2026-87857: Temporal Server does not bind a workflow-history pagination token to the namespace and workflow named

Source GCVE Database

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Authoritative record:CVE-2026-87857· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 1.31.3 or 1.30.7 when convenient.

Data as of 9 Nov 2026, 22:20 UTC

CVSS 4.0 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (Temporal)	CVSS 4.0	5.3

Patch: Available – fixed in 1.31.3, 1.30.7

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: Low
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-fqqw-cv9m-h3p6

What to do

Upgrade Temporal Server and go.temporal.io/server to 1.31.3 or 1.30.7.

Affected software

Product	Affected	Fixed in
Temporal Servergo.temporal.io/server	Affected >=1.0.0 <=1.29.7 >=1.30.0 <1.30.7 >=1.31.0 <1.31.3	Fixed in 1.31.3 1.30.7
Gogo.temporal.io/server`pkg:golang/go.temporal.io/server`Other threats	Affected >=1.0.0 <=1.29.7 >=1.30.0 <1.30.7 >=1.31.0 <1.31.3	Fixed in 1.30.7 1.31.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

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.

CWE-639Authorization Bypass Through User-Controlled Key (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #24OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
Architecture and Design
For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
Architecture and Design · Implementation
Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
Architecture and Design
Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
OWASP Cheat Sheets
Access Control (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Insecure Direct Object Reference Prevention (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V4.1.2 (opens in a new tab)
V4.2.1 (opens in a new tab)
V8.3.8 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Affected software

Description

WeaknessesCWE-639

Technical details

References

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