# CVE-2026-21883: Bokeh server applications have Incomplete Origin Validation in WebSockets

> Attackers can bypass WebSocket origin checks to access or modify Bokeh server data if an allowlist is configured.

- **Severity:** Medium 4.5 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 8 Jan 2026
- **Updated:** 23 Jan 2026
- **Also known as:** GHSA-793v-589g-574v, PYSEC-2026-1223

## What is CVE-2026-21883?

CVE-2026-21883 is a medium-severity missing authorization vulnerability in bokeh, published on 8 Jan 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Bokeh is an interactive visualization library written in Python. In versions 3.8.1 and below, if a server is configured with an allowlist (e.g., dashboard.corp), an attacker can register a domain like dashboard.corp.attacker.com (or use a subdomain if applicable) and lure a victim to visit it. The malicious site can then initiate a WebSocket connection to the vulnerable Bokeh server. Since the Origin header (e.g., http://dashboard.corp.attacker.com/) matches the allowlist according to the flawed logic, the connection is accepted. Once connected, the attacker can interact with the Bokeh server on behalf of the victim, potentially accessing sensitive data, or modifying visualizations. This issue is fixed in version 3.8.2.

Weakness: CWE-1385 (Missing Origin Validation in WebSockets)

## Which versions are affected by CVE-2026-21883?

3 open source packages ship an affected version, including bokeh. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `bokeh` | PyPI | All versions | 3.8.2 |
| `bokeh` | PyPI | All versions | 3.8.2 |
| `bokeh` | PyPI | All versions | 3.8.2 |

Products: Bokeh Bokeh.

## How do I fix CVE-2026-21883?

Upgrade bokeh to 3.8.2 or later.

## Is CVE-2026-21883 being exploited?

There is no known exploitation of CVE-2026-21883 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-21883 and fix it if it is affected.

What it is: CVE-2026-21883 is a medium-severity missing authorization vulnerability in bokeh, published on 8 Jan 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-21883 in the wild and no public exploit code.

Affected packages and fixed versions:
- bokeh (PyPI): affected all versions; fixed in 3.8.2
- bokeh (PyPI): affected all versions; fixed in 3.8.2
- bokeh (PyPI): affected all versions; fixed in 3.8.2

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-2026-21883/ (Markdown: https://insights.sbomify.com/CVE-2026-21883/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-21883
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-21883
- OSV: https://osv.dev/vulnerability/CVE-2026-21883

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-21883/
Summaries are generated and may contain mistakes; the official description above is the record.