# CVE-2026-53904: Account Denial of Service in MCO

> Attackers can lock victims out of MCO accounts by repeatedly triggering password resets, causing account denial of service.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Jul 2026
- **Updated:** 1 Jul 2026
- **Also known as:** GHSA-4p9c-w7qw-q5pq

## What is CVE-2026-53904?

CVE-2026-53904 is a medium-severity denial of service vulnerability in MyComplianceOffice MCO, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

MCO is vulnerable to Account Denial of Service due to improper implementation of password reset functionality. Each password reset request invalidates previously set password as well as previously issued temporary passwords, furthermore, password resets are not limited in any way. An attacker who provides victim's email and answer to their security question, can successfully initiate the reset process and continuously invalidate credentials, effectively locking the victim out of their account. Answering security questions has a limited number of tries which lowers the risk of this vulnerability.

Because vendor contact attempts were unsuccessful, the vulnerability has only been confirmed in version 25.3.3.1 but may also affect other versions.

Weakness: CWE-640 (Weak Password Recovery Mechanism for Forgotten Password), CWE-307 (Improper Restriction of Excessive Authentication Attempts)

## Which versions are affected by CVE-2026-53904?

It affects 1 product.


Products: Mycomplianceoffice Mco.

## How do I fix CVE-2026-53904?

No fix has been published for CVE-2026-53904 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-53904 being exploited?

There is no known exploitation of CVE-2026-53904 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53904 and fix it if it is affected.

What it is: CVE-2026-53904 is a medium-severity denial of service vulnerability in MyComplianceOffice MCO, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-53904 in the wild and no public exploit code.

Affected product: MyComplianceOffice MCO. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-53904/ (Markdown: https://insights.sbomify.com/CVE-2026-53904/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53904
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53904
- OSV: https://osv.dev/vulnerability/CVE-2026-53904

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53904/
Summaries are generated and may contain mistakes; the official description above is the record.