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Fencer Vulns
medium 5.4

CVE-2026-21883 json

Bokeh server applications have Incomplete Origin Validation in WebSockets

published 2026-01-06 10 mo ago modified 2026-09-10 1 mo ago also GHSA-793v-589g-574v , PYSEC-2026-1223 , EUVD-2026-1036

cvss
5.4
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 7%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi bokeh 3.8.2
  • bokeh bokeh 3.8.2

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-21883 updated cvss 5.4

Bokeh: Bokeh: Information disclosure and unauthorized actions via flawed WebSocket origin validation

  • Red Hat OpenShift AI (RHOAI) rhoai/odh-workbench-jupyter-pytorch-cuda-py312-rhel9, rhoai/odh-workbench-jupyter-pytorch-rocm-py312-rhel9, rhoai/odh-workbench-jupyter-trustyai-cpu-py312-rhel9, rhoai/odh-workbench-jupyter-datascience-cpu-py312-rhel9, rhoai/odh-workbench-jupyter-tensorflow-cuda-py312-rhel9, rhoai/odh-workbench-jupyter-tensorflow-rocm-py312-rhel9, +1 more
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
10 mo ago

Exploit prediction

0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/bokeh/bokeh/security/advisories/GHSA-793v-589g-574v referenced PoC, tagged "exploit" by a source, unverified
  • aydinnyunus.github.io https://aydinnyunus.github.io/2026/01/24/bokeh-websocket-hijacking-cve-2026-21883/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 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
CNA 4.0 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/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
NVD 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
pypi bokeh
<3.8.2
3.8.2

Affected products

  • bokeh bokeh

Classification

Weakness
  • CWE-1385 Missing Origin Validation in WebSockets

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.