CVE-2026-89140

6.0Medium

Published 12 Oct 2026 · NVD status: Awaiting Analysis · AI triage by gemini-3.8-flash

6.0Medium

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None
Impact: High impact on integrity
Weakness: CWE-639

Impact

An authenticated user with write access in one namespace can tamper with Scheduler V2 schedule states in another namespace, bypassing overlap policies or injecting inputs into subsequent workflow runs. The attacker needs valid credentials in at least one namespace plus knowledge of the target namespace, schedule ID, and running action timing.

Root cause

The History service fails to bind internal completion callbacks to the originating namespace and does not validate authorization when delivering reserved 'temporal://internal' callbacks across namespaces.

Affected systems

Temporal Server versions prior to 1.30.8, 1.31.4, and 1.32.1 where Scheduler V2 is or was enabled.

CVSS v4.0 · CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/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

Fix & remediation

Upgrade Temporal Server to 1.30.8, 1.31.4, 1.32.1, or later. If upgrading must wait, note that disabling the setting that creates Scheduler V2 schedules does not protect existing ones; avoid granting untrusted callers write access to any namespace on the cluster.

AI-suggested. Run it in staging first and check it against the vendor advisory. Why?

Ad · In-content banner

NVD description

Temporal Server does not bind internal completion callbacks to the namespace that attached them, which allows an authenticated caller with write permission in one namespace to alter Scheduler V2 schedule state in another namespace. The callback address temporal://internal is reserved for callbacks that Scheduler V2 attaches to the Workflows it starts. In affected releases, any authenticated caller could attach a callback with that address to a Workflow start request, the address was exempt from the component.callbacks.allowedAddresses allowlist, and the History service delivered the callback to the component its token named, in whatever namespace that was, without authorizing the original caller there. When the forged completion matches an action a target schedule is running, the schedule records the action as completed while its Workflow still runs, which can defeat an overlap policy such as SKIP, and passes caller-controlled data to the next scheduled Workflow as its last completion result. A forged failure may also pause a schedule configured to pause on failure. A forgery requires the target namespace identifier, the schedule identifier, and the identity and timing of a running action. No disclosure of Workflow payloads or history was identified. Only namespaces that hold Scheduler V2 schedules can be targeted; Scheduler V2 is off by default, and existing Scheduler V2 schedules remain targets after the settings that create them are turned off.

References

Source: nvd.nist.gov/vuln/detail/CVE-2026-89140