CVE-2020-10185Network attack vector

OTP replay via inconsistent sync parameter validation

Published Mar 5, 2020 · Updated Aug 4, 2024

Authentication bypass in Yubico YubiKey Validation Server before 2.40 allows remote attackers to replay a previously used OTP. The sync endpoint executes database operations on inconsistently validated parameters, allowing an accepted sync peer to reintroduce an OTP that the service has already consumed. Exposure requires a self-hosted instance with an allowed source in the non-default sync pool; YubiCloud and Yubico devices are unaffected.

CVSS severity8.6
High
EPSS probability1.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Authentication bypass in Yubico YubiKey Validation Server before 2.40 allows remote attackers to replay a previously used OTP. The sync endpoint executes database operations on inconsistently validated parameters, allowing an accepted sync peer to reintroduce an OTP that the service has already consumed. Exposure requires a self-hosted instance with an allowed source in the non-default sync pool; YubiCloud and Yubico devices are unaffected.

The record

CVE
CVE-2020-10185
Published
Mar 5, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-294, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 5, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
8.6NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-294Authentication Bypass by Capture-replay
T1078Valid Accounts

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo