CVE-2013-2566
MEDIUMEPSS 100th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Exploit Intelligence
Very high risk: more likely to be exploited than 100% of all known CVEs.
References
Related Vulnerabilities
Other CWE-326 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2014-0224 | High | 7.4 | 95% | - | Fix |
| CVE-2017-1000486 | Critical | 9.8 | 94% | KEV | Fix |
| CVE-2017-11317 | Critical | 9.8 | 83% | KEV | - |
| CVE-2018-18325 | High | 7.5 | 74% | KEV | - |
| CVE-2018-15811 | High | 7.5 | 74% | KEV | - |
| CVE-2011-3389 | Medium | 4.3 | 73% | - | Fix |
Common questions
How do I fix CVE-2013-2566?
Published advisories record a fix for 3 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2013-2566 being actively exploited?
Not that we know of. CVE-2013-2566 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 84.4% is the estimated probability that it will be exploited in the next 30 days. That is higher than 100% of all scored CVEs.
How severe is CVE-2013-2566?
CVE-2013-2566 has a CVSS v3 base score of 5.9, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2013-2566 affect?
Published advisories record a fix for DeveloperEdition (Windows application), Mozilla Firefox (en-US) (Windows application), Mozilla Thunderbird (en-US) (Windows application). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-29.