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.
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.002 (6.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 6.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000
Affected products
- Bokeh — versions < 3.8.2
Weakness classification (CWE)
References
- github.com/bokeh/bokeh/security/advisories/GHSA-793v-589g-574v (Exploit, Vendor Advisory)
- github.com/bokeh/bokeh/commit/cedd113b0e271b439dce768671685cf5f861812e (Patch)
- 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.