# CVE-2013-2566: Weak cryptography in n/a

> Remote attackers can recover plaintext from TLS/SSL sessions using RC4 due to statistical biases, requiring disabling RC4 ciphers.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Mar 2013
- **Updated:** 22 May 2026
- **Also known as:** GHSA-f67x-vqh9-8p43

## What is CVE-2013-2566?

CVE-2013-2566 is a medium-severity vulnerability in Canonical Ubuntu Linux, published on 14 Mar 2013. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The RC4 algorithm, as used in the TLS protocol and SSL protocol, has many single-byte biases, which makes it easier for remote attackers to conduct plaintext-recovery attacks via statistical analysis of ciphertext in a large number of sessions that use the same plaintext.

Weakness: CWE-326 (Inadequate Encryption Strength), CWE-327 (Use of a Broken or Risky Cryptographic Algorithm)

## Which versions are affected by CVE-2013-2566?

It affects 16 products.


Products: Canonical Ubuntu Linux, Fujitsu M10-1 Firmware, Fujitsu M10-4 Firmware, Fujitsu M10-4s Firmware, Fujitsu Sparc Enterprise M3000 Firmware, Fujitsu Sparc Enterprise M4000 Firmware, Fujitsu Sparc Enterprise M5000 Firmware, Fujitsu Sparc Enterprise M8000 Firmware, Fujitsu Sparc Enterprise M9000 Firmware, Mozilla Firefox, Mozilla Seamonkey, Mozilla Thunderbird, Mozilla Thunderbird Esr, Oracle Communications Application Session Controller, Oracle Http Server, Oracle Integrated Lights Out Manager Firmware.

## How do I fix CVE-2013-2566?

Change a configuration setting.

## Is CVE-2013-2566 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2013-2566 exists.

Public exploit code:

- SSL/TLS Version Detection (metasploit)

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2013-2566 and fix it if it is affected.

What it is: CVE-2013-2566 is a medium-severity vulnerability in Canonical Ubuntu Linux, published on 14 Mar 2013. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2013-2566 exists.

Affected product: Canonical Ubuntu Linux. 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-2013-2566/ (Markdown: https://insights.sbomify.com/CVE-2013-2566/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2013-2566
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2013-2566
- OSV: https://osv.dev/vulnerability/CVE-2013-2566

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From sbomify Insights: https://insights.sbomify.com/CVE-2013-2566/
Summaries are generated and may contain mistakes; the official description above is the record.