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HIGH severity

CVE-2020-27178 — cas-server-webapp

HIGH

CVE-2020-27178 is a high-severity (CVSS 7.5) vulnerability in org.apereo.cas:cas-server-webapp. A fix is available for org.apereo.cas:cas-server-webapp — see the affected versions and patch details below.

Improper Authentication in Apereo CAS

Also known asGHSA-q39c-5vh5-vw2p
Published
Updated
Affected
6 pkgs
Patched
6 / 6
Exploits
None indexed
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs68th percentile — riskier than 68% of all scored CVEsHighest risk
0.00%0.57%1.15%1.72%0.2%1.2%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2020-27178 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

6 pkgs affected
☕org.apereo.cas:cas-server-webapp☕org.apereo.cas:cas-server-webapp☕org.apereo.cas:cas-server-webapp☕org.apereo.cas:cas-server-support-otp-mfa-core☕org.apereo.cas:cas-server-support-otp-mfa-core☕org.apereo.cas:cas-server-support-otp-mfa-core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Apereo CAS 5.3.x before 5.3.16, 6.x before 6.1.7.2, 6.2.x before 6.2.4, and 6.3.x before 6.3.0-RC4 mishandles secret keys with Google Authenticator for multifactor authentication.

Affected Packages

6 total 6 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.apereo.cas:cas-server-webapp≥ 5.3.0&&< 5.3.165.3.16org.apereo.cas:cas-server-webapp:5.3.16
☕Mavenorg.apereo.cas:cas-server-webapp≥ 6.0.0&&< 6.1.7.26.1.7.2org.apereo.cas:cas-server-webapp:6.1.7.2
☕Mavenorg.apereo.cas:cas-server-webapp≥ 6.2.0&&< 6.2.46.2.4org.apereo.cas:cas-server-webapp:6.2.4
☕Mavenorg.apereo.cas:cas-server-support-otp-mfa-core≥ 5.3.0&&< 5.3.165.3.16org.apereo.cas:cas-server-support-otp-mfa-core:5.3.16
☕Mavenorg.apereo.cas:cas-server-support-otp-mfa-core≥ 6.0.0&&< 6.1.7.26.1.7.2org.apereo.cas:cas-server-support-otp-mfa-core:6.1.7.2
☕Mavenorg.apereo.cas:cas-server-support-otp-mfa-core≥ 6.2.0&&< 6.2.46.2.4org.apereo.cas:cas-server-support-otp-mfa-core:6.2.4

Affected Products

1 product · 6 configurations
Application
central authentication serviceapereo
≥ 6.2.0 && < 6.2.4
1 version
6.3.0

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update org.apereo.cas:cas-server-webapp to 5.3.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-27178 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Apereo CAS 5.3.x before 5.3.16, 6.x before 6.1.7.2, 6.2.x before 6.2.4, and 6.3.x before 6.3.0-RC4 mishandles secret keys with Google Authenticator for multifactor authentication.
O3 Security · Impact-Aware SCA

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CVE-2020-27178: cas-server-webapp — Fixed in 5.3.16