CVE-2026-56278: Flowise - Session Hijacking via Weak Default Express Session Secret
Flowise before 3.1.0 (affected versions 3.0.13 and earlier) uses a weak hardcoded default secret ('flowise') for the express-session middleware when the EXPRESSSESSIONSECRET environment variable is not set (packages/server/src/enterprise/middleware/passport/index.ts). Because this default secret is publicly visible in the source code, an attacker can forge valid signed session cookies to impersonate any user and bypass authentication.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Flowiseto a version that resolves this vulnerability.Fixed in 3.1.0 - Configuration
Set the EXPRESS_SESSION_SECRET environment variable to a strong, unique value so express-session does not fall back to the weak hardcoded default secret ('flowise').
Flowise (express-session / passport middleware) EXPRESS_SESSION_SECRET = Set to a strong, unique secret (do not leave unset)
Event History
Frequently Asked Questions
What is the severity of CVE-2026-56278?
CVE-2026-56278 has a severity rating of critical with a score of 9.3.
How do I fix CVE-2026-56278?
To fix CVE-2026-56278, set a strong custom value for the EXPRESS_SESSION_SECRET environment variable.
What versions of Flowise are affected by CVE-2026-56278?
CVE-2026-56278 affects Flowise versions 3.0.13 and earlier.
What type of vulnerability is CVE-2026-56278?
CVE-2026-56278 is a session hijacking vulnerability due to a weak default secret.
What conditions trigger CVE-2026-56278?
CVE-2026-56278 is triggered when the EXPRESS_SESSION_SECRET environment variable is not set.