CVE-2026-28787: OneUptime WebAuthn 2FA bypass via client-supplied challenge

CVE-2026-28787 · Severity: low · CVSS 3.1 · Published 2026-03-02

OneUptime is an open-source monitoring and incident management platform that uses WebAuthn (hardware security keys and biometric authentication) as a second-factor authentication method. The vulnerability allows attackers who possess a user's password and a captured authentication assertion to bypass 2FA entirely and gain full account access. An attacker can replay a single captured assertion indefinitely, rendering WebAuthn's security protection ineffective.

Technologies: @oneuptime/common (npm), OneUptime. Vendors: npm, OneUptime.

Quick answers

Is CVE-2026-28787 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-28787 being exploited in the wild.
How severe is CVE-2026-28787?
Low severity, with a CVSS score of 3.1, published 2 March 2026.
Which products and versions are affected?
@oneuptime/common (npm) SEMVER:introduced=0,last_affected=10.0.11; OneUptime <= 10.0.11.
Is there a fix for CVE-2026-28787?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-28787 attacked?
It is attacked over the network.
Am I affected by CVE-2026-28787?
Check whether you run @oneuptime/common (npm) or OneUptime at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability is an authentication bypass in the WebAuthn verification flow. The server generates a challenge during authentication initiation but never stores it server-side (violating the W3C WebAuthn specification). Instead, it accepts the challenge value directly from the client request body during credential verification. Since both the expected challenge and the challenge signed by the authenticator come from the same captured assertion, they always match, allowing an attacker to replay a previously captured valid WebAuthn assertion indefinitely. Exploitation requires the attacker to already possess the victim's password and a valid WebAuthn assertion (obtainable via XSS, network interception, or log exposure). The fix requires storing the challenge server-side (in session or database) and comparing the client-provided challenge against the stored value rather than the client-supplied value. As of the advisory publication, no patched version was available.

Affected products

  • OneUptime OneUptime <= 10.0.11

Identifiers

  • CVE-2026-28787
  • GHSA-gjjc-pcwp-c74m

Timeline

  • 2026-03-02: disclosed: Advisory published
  • 2026-03-02: advisory: GHSA-gjjc-pcwp-c74m and CVE-2026-28787 assigned

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.