CVE-2020-10185 — The sync endpoint in YubiKey Validation Server before 2

The sync endpoint in YubiKey Validation Server before 2.40 allows remote attackers to replay an OTP. NOTE: this issue is potentially relevant to persons outside Yubico who operate a self-hosted OTP validation service with a non-default configuration such as an open sync pool; the

01What is this vulnerability?

The sync endpoint in YubiKey Validation Server before 2.40 allows remote attackers to replay an OTP. NOTE: this issue is potentially relevant to persons outside Yubico who operate a self-hosted OTP validation service with a non-default configuration such as an open sync pool; the issue does NOT affect YubiCloud.

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: 2020-03-05T22:48:14.000Z
• Last modified: 2024-08-04T10:58:39.520Z

09References

• www.yubico.com — https://www.yubico.com/support/security-advisories/ysa-2020-01/
• github.com — https://github.com/Yubico/yubikey-val/releases/tag/yubikey-val-2.40
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2020/03/msg00014.html