Improper Authentication in Apereo CAS

published 2020-10-16 6y ago modified 2026-06-17 4mo ago also GHSA-q39c-5vh5-vw2p , EUVD-2021-1832

cvss: 7.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.2%; EPSS 1.2% chance of exploitation in 30 days, percentile 68%
public exploits: 0; none known

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.

Patch / fix

fixed in 3

maven org.apereo.cas:cas-server-webapp 5.3.16, 6.1.7.2, 6.2.4
maven org.apereo.cas:cas-server-support-otp-mfa-core 5.3.16, 6.1.7.2, 6.2.4
apereo central_authentication_service 5.3.16, 6.1.7.2, 6.2.4

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Exploit prediction

1.22% chance of exploitation in the next 30 days, higher than 68% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N
GitHub	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem	package	affected	fixed in
maven	org.apereo.cas:cas-server-webapp	>=5.3.0, <5.3.16 >=6.0.0, <6.1.7.2 >=6.2.0, <6.2.4	5.3.16 6.1.7.2 6.2.4
maven	org.apereo.cas:cas-server-support-otp-mfa-core	>=5.3.0, <5.3.16 >=6.0.0, <6.1.7.2 >=6.2.0, <6.2.4	5.3.16 6.1.7.2 6.2.4

Classification

Weakness

CWE-287 Improper Authentication

References

apereo.github.io /2020/10/14/gauthvuln/
vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2020-27178
advisory
apereo.github.io /2020/10/14/gauthvuln
web

Sources

Fencer Intel 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.