CVE-2019-19521 — libc in OpenBSD 6

libc in OpenBSD 6.6 allows authentication bypass via the -schallenge username, as demonstrated by smtpd, ldapd, or radiusd. This is related to gen/auth_subr.c and gen/authenticate.c in libc (and login/login.c and xenocara/app/xenodm/greeter/verify.c).

01What is this vulnerability?

libc in OpenBSD 6.6 allows authentication bypass via the -schallenge username, as demonstrated by smtpd, ldapd, or radiusd. This is related to gen/auth_subr.c and gen/authenticate.c in libc (and login/login.c and xenocara/app/xenodm/greeter/verify.c).

02Affected products

Vendor	Product	Versions
n	a / n/a	n/a

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2019-12-04T23:33:35.000Z
• Last modified: 2024-08-05T02:16:47.981Z

09References

• www.openwall.com — https://www.openwall.com/lists/oss-security/2019/12/04/5
• www.openbsd.org — https://www.openbsd.org/errata66.html
• www.openwall.com — http://www.openwall.com/lists/oss-security/2019/12/04/6
• www.openwall.com — http://www.openwall.com/lists/oss-security/2019/12/04/5
• seclists.org — https://seclists.org/bugtraq/2019/Dec/8
• packetstormsecurity.com — http://packetstormsecurity.com/files/155572/Qualys-Security-Advisory-OpenBSD-Aut…
• seclists.org — http://seclists.org/fulldisclosure/2019/Dec/14