# CVE-2026-28787: OneUptime has WebAuthn 2FA bypass: server accepts client-supplied challenge instead of server-stored value, allowing credential replay

> Attackers can bypass WebAuthn 2FA by replaying captured assertions because the server fails to validate the challenge against a stored value.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Mar 2026
- **Updated:** 9 Mar 2026
- **Also known as:** GHSA-gjjc-pcwp-c74m

## What is CVE-2026-28787?

CVE-2026-28787 is a high-severity authentication bypass vulnerability in oneuptime, published on 6 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

OneUptime is a solution for monitoring and managing online services. In version 10.0.11 and prior, the WebAuthn authentication implementation does not store the challenge on the server side. Instead, the challenge is returned to the client and accepted back from the client request body during verification. This violates the WebAuthn specification (W3C Web Authentication Level 2, §13.4.3) and allows an attacker who has obtained a valid WebAuthn assertion (e.g., via XSS, MitM, or log exposure) to replay it indefinitely, completely bypassing the second-factor authentication. No known patches are available.

Weakness: CWE-294 (Authentication Bypass by Capture-replay), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-28787?

2 open source packages ship an affected version, including @oneuptime/common. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@oneuptime/common` | npm | All versions to 10.0.11 | None |
| `@oneuptime/common` | npm | All versions to 10.0.11 | None |

Products: Hackerbay Oneuptime.

## How do I fix CVE-2026-28787?

No fix has been published for CVE-2026-28787 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-28787 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-28787 exists.

## Other vulnerabilities in oneuptime

- [CVE-2026-33396](https://insights.sbomify.com/CVE-2026-33396/): Code injection in oneuptime (critical 10.0)
- [CVE-2026-32306](https://insights.sbomify.com/CVE-2026-32306/): OneUptime ClickHouse SQL Injection via Aggregate Query Parameters (critical 10.0)
- [CVE-2026-30956](https://insights.sbomify.com/CVE-2026-30956/): OneUptime has authorization bypass via client‑controlled is-multi-tenant-query header (critical 10.0)
- [CVE-2026-30957](https://insights.sbomify.com/CVE-2026-30957/): OneUptime Synthetic Monitor RCE via exposed Playwright browser object (critical 10.0)
- [CVE-2026-30887](https://insights.sbomify.com/CVE-2026-30887/): OneUptime Affected by Unsandboxed Code Execution in Probe Allows Any Project Member to Achieve RCE (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-28787 and fix it if it is affected.

What it is: CVE-2026-28787 is a high-severity authentication bypass vulnerability in oneuptime, published on 6 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-28787 exists.

Affected packages and fixed versions:
- @oneuptime/common (npm): affected all versions up to 10.0.11; no fix listed
- @oneuptime/common (npm): affected all versions up to 10.0.11; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-28787/ (Markdown: https://insights.sbomify.com/CVE-2026-28787/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-28787
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-28787
- OSV: https://osv.dev/vulnerability/CVE-2026-28787

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-28787/
Summaries are generated and may contain mistakes; the official description above is the record.