Vulnerability in Bokeh
CVE-2026-21883
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.
EPSS: 0.002 (5.3th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.
Affected products
- Bokeh — versions < 3.8.2
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- af854a3a-2127-422b-91ae-364da2661108 (Exploit, Mitigation, Third Party Advisory)
Frequently asked questions
- What is CVE-2026-21883?
- CVE-2026-21883 is a medium-severity vulnerability in Bokeh, classified under CWE-1385. CVSS score: 5.4/10. Published 2026-01-08.
- How severe is CVE-2026-21883?
- Medium severity. CVSS v3 base score is 5.4 out of 10.