CVE-2026-21883
Bokeh ≤ 3.8.2
Raw vector
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:XSummary
CVE-2026-21883 is a medium-severity Missing Origin Validation in WebSockets (CWE-1385) vulnerability in Bokeh Bokeh. Its CVSS base score is 4.5 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Browser Session Hijacking (T1185); ranked at the 6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and AC-4 (Information Flow Enforcement) — see the control section below for these in your framework.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-1036
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V4.4.2
Mitigating Controls (NIST 800-53 r5) AI
Enforces approved authorizations on logical access, which can include origin checks before accepting WebSocket connections.
Enforces information flow policies that can require validation of communication origins at system boundaries.
Protects authenticity of communications sessions, which origin validation helps ensure for WebSocket handshakes.
Monitors and controls communications at external interfaces, directly supporting origin validation for inbound WebSocket traffic.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require origin validation for WebSocket endpoints.
Origin validation is a required step when authenticating WebSocket connection requests.
Enforcing authorization policy on incoming connections can require origin checks.
Network-level controls that block unauthorized logical access can mitigate missing origin checks.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect missing origin validation in WebSocket implementations.
Network security controls can enforce origin validation and restrict WebSocket connections to trusted sources.
Secure configuration of network services can include origin checks for WebSocket endpoints.
Application security requirements can mandate origin validation for WebSocket communications.
Secure architecture principles can require proper origin validation mechanisms in WebSocket implementations.
Secure coding standards can explicitly require origin validation for WebSocket connections.