# CVE-2026-5199: Cross Namespace Access via Batch Operation

> Attackers can manipulate workflows in other namespaces if cross-namespace authorization is enabled, requiring specific IDs and names.

- **Severity:** Low 2.3 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:L/SA:L/S:N/AU:Y/R:U/RE:M`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Apr 2026
- **Updated:** 1 Apr 2026
- **Also known as:** CLEANSTART-2026-BV78886, CLEANSTART-2026-DE80520, CLEANSTART-2026-LH40285, ECHO-7744-7b2d-d504, GHSA-xpg8-3hhp-p7w8, GO-2026-5766, MINI-2x2h-68jm-2hc8, MINI-3r9x-gpvj-cf5g, MINI-8v96-x5m6-v37q, MINI-jc5p-cjjx-hjh3, MINI-q3g3-vrpc-q28m, MINI-qf84-6c97-696v, MINI-v7rw-f98r-4mq7, MINI-x9jw-4vr3-5gg7

## What is CVE-2026-5199?

CVE-2026-5199 is a low-severity missing authorization vulnerability in temporal, published on 1 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A writer role user in an attacker-controlled namespace could signal, delete, and reset workflows or activities in a victim namespace on the same cluster. Exploitation requires the attacker to know or guess specific victim workflow ID(s) and, for signal operations, signal names. This was due to a bug introduced in Temporal Server v1.29.0 which inadvertently allowed an attacker to control the namespace name value instead of using the server's own trusted name value within the batch activity code. The batch activity validated the namespace ID but did not cross-check the namespace name against the worker's bound namespace, allowing the per-namespace worker's privileged credentials to operate on an arbitrary namespace. Exploitation requires a server configuration where internal components have cross-namespace authorization, such as deployment of the internal-frontend service or equivalent TLS-based authorization for internal identities.

This vulnerability also impacted Temporal Cloud when the attacker and victim namespaces were on the same cell, with the same preconditions as self-hosted clusters.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-5199?

5 open source packages ship an affected version, including go.temporal.io/server.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `go.temporal.io/server` | Go | All versions | 1.29.5, 1.30.3 |
| `go.temporal.io/server` | Go | All versions | 1.29.5 |
| `go.temporal.io/server` | Go | All versions | 1.29.5 |
| `go.temporal.io/server` | Go | From 1.30.0-143.0 | 1.30.3 |
| `go.temporal.io/server` | Go | From 1.30.0-143.0 | 1.30.3 |

## How do I fix CVE-2026-5199?

Upgrade go.temporal.io/server to a fixed version for your release line: 1.29.5 or 1.30.3.

## Is CVE-2026-5199 being exploited?

There is no known exploitation of CVE-2026-5199 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-5199 and fix it if it is affected.

What it is: CVE-2026-5199 is a low-severity missing authorization vulnerability in temporal, published on 1 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-5199 in the wild and no public exploit code.

Affected packages and fixed versions:
- go.temporal.io/server (Go): affected all versions; fixed in 1.29.5, 1.30.3
- go.temporal.io/server (Go): affected all versions; fixed in 1.29.5
- go.temporal.io/server (Go): affected all versions; fixed in 1.29.5
- go.temporal.io/server (Go): affected from 1.30.0-143.0; fixed in 1.30.3
- go.temporal.io/server (Go): affected from 1.30.0-143.0; fixed in 1.30.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-5199/ (Markdown: https://insights.sbomify.com/CVE-2026-5199/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-5199
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-5199
- OSV: https://osv.dev/vulnerability/CVE-2026-5199

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-5199/
Summaries are generated and may contain mistakes; the official description above is the record.