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📦
📦 npm
Not in CISA KEV
HIGH severity

CVE-2021-39171 — passport-saml

HIGHFix: node-saml/passport-saml#595

CVE-2021-39171 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in passport-saml. A fix is available for passport-saml — see the affected versions and patch details below.

Unlimited transforms allowed for signed nodes

Also known asGHSA-5379-r78w-42h2
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs71th percentile — riskier than 71% of all scored CVEsHighest risk
0.00%0.61%1.22%1.82%0.5%1.3%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.

passport-samlnpm
87Kdownloads / week

Description

Passport-SAML is a SAML 2.0 authentication provider for Passport, the Node.js authentication library. Prior to version 3.1.0, a malicious SAML payload can require transforms that consume significant system resources to process, thereby resulting in reduced or denied service. This would be an effective way to perform a denial-of-service attack. This has been resolved in version 3.1.0. The resolution is to limit the number of allowable transforms to 2.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmpassport-samlall versions3.1.0npm install passport-saml@3.1.0

Affected Products

1 product · 1 configurations
Application
passport-samlpassport-saml_project
< 3.1.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for passport-saml, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update passport-saml to 3.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39171 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

Passport-SAML is a SAML 2.0 authentication provider for Passport, the Node.js authentication library. Prior to version 3.1.0, a malicious SAML payload can require transforms that consume significant system resources to process, thereby resulting in reduced or denied service. This would be an effective way to perform a denial-of-service attack. This has been resolved in version 3.1.0. The resolution is to limit the number of allowable transforms to 2.
O3 Security · Impact-Aware SCA

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CVE-2021-39171: passport-saml — Fixed in 3.1.0