CVE-2013-2566

MEDIUMNVD 5.99.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because EPSS predicts 93% probability of exploitation within the next 30 days (top 0.2% of all CVEs). NVD baseline CVSS 5.9 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction ≥85%
Sources: epss, ghsa, nvd
Weaponized
5.9
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 84%
CISA-KEV: Not listedEPSS: 84%CVSS: 5.9Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
5.9
EG Score
9.0(high)
EPSS
99.7%
KEV
Not listed

Published

March 15, 2013

Last Modified

May 22, 2026

Advisory Details (5)

Auto-updated May 29, 2026
No patch confirmed yet.
generic

Mozilla Network Security Service: Multiple vulnerabilities (GLSA 201406-19) — Gentoo security

http://security.gentoo.org/glsa/glsa-201406-19.xml
generic

The Opera Blog - News | Opera

http://my.opera.com/securitygroup/blog/2013/03/20/on-the-precariousness-of-rc4
generic

'[security bulletin] HPSBGN03324 rev.1 - HP Business Service Automation Essentials Core, Remote Discl' - MARC

http://marc.info/?l=bugtraq&m=143039468003789&w=2
generic

CEC Juniper Community

http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10705
generic

Attack of the week: RC4 is kind of broken in TLS – A Few Thoughts on Cryptographic Engineering

http://blog.cryptographyengineering.com/2013/03/attack-of-week-rc4-is-kind-of-broken-in.html

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntufirefox (25.0.1+build1-0ubuntu0.13.10.1) @ saucy2026-05-29ubuntu
ubuntuthunderbird (1:24.1.1+build1-0ubuntu0.13.04.1) @ raring2026-05-29ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 4× in last 7d / 13× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 14:04 UTCEPSS rescore
  2. 2026-07-22 14:04 UTCEPSS rescore
  3. 2026-07-21 15:21 UTCEPSS rescore
  4. 2026-07-18 10:00 UTCEPSS rescore
  5. 2026-07-15 16:54 UTCEPSS rescore
  6. 2026-07-15 16:54 UTCEPSS rescore
  7. 2026-07-09 19:05 UTCEPSS rescore
  8. 2026-07-04 06:27 UTCEPSS rescore
  9. 2026-06-28 04:53 UTCEPSS rescore
  10. 2026-06-28 04:53 UTCEPSS rescore
  11. 2026-06-24 14:02 UTCEPSS rescore
  12. 2026-06-24 14:02 UTCEPSS rescore
  13. 2026-06-23 21:30 UTCEPSS rescore
  14. 2026-06-18 17:49 UTCEPSS rescore
  15. 2026-06-18 17:49 UTCEPSS rescore
  16. 2026-06-16 17:49 UTCEPSS rescore
  17. 2026-06-16 17:49 UTCEPSS rescore
  18. 2026-06-15 17:44 UTCEPSS rescore
  19. 2026-06-13 22:57 UTCEPSS rescore
  20. 2026-06-12 23:08 UTCEPSS rescore
  21. 2026-06-05 22:44 UTCEPSS rescore
  22. 2026-06-05 22:44 UTCEPSS rescore
  23. 2026-06-02 20:10 UTCEPSS rescore
  24. 2026-06-02 20:10 UTCEPSS rescore
  25. 2026-05-29 00:36 UTCEG score recompute
Show 14 more
  1. 2026-05-29 00:36 UTCVendor advisory
  2. 2026-05-29 00:36 UTCGHSA enrichment
  3. 2026-05-26 13:41 UTCEPSS rescore
  4. 2026-05-26 13:41 UTCEPSS rescore
  5. 2026-05-24 16:43 UTCEPSS rescore
  6. 2026-05-22 21:15 UTCEPSS rescore
  7. 2026-05-22 21:15 UTCEPSS rescore
  8. 2026-05-22 21:15 UTCEPSS rescore
  9. 2026-05-21 22:39 UTCEPSS rescore
  10. 2026-05-20 11:21 UTCEPSS rescore
  11. 2026-05-20 11:21 UTCEPSS rescore
  12. 2026-05-20 11:21 UTCEPSS rescore
  13. 2026-05-18 21:29 UTCEPSS rescore
  14. 2026-05-18 21:29 UTCEPSS rescore

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 Metasploit module). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Metasploitauxiliary/scanner/ssl/ssl_version✓ verified
    First seen Oct 14, 2014

    SSL/TLS Version Detection

    Open source ↗

Frequently asked(5)

What is CVE-2013-2566?
CVE-2013-2566 is a medium vulnerability published on March 15, 2013. 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.
When was CVE-2013-2566 disclosed?
CVE-2013-2566 was first published in the National Vulnerability Database on March 15, 2013, with the most recent update on May 22, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2013-2566 actively exploited?
CVE-2013-2566 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 99.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2013-2566?
CVE-2013-2566 has a CVSS v3 base score of 5.9 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
How do I remediate CVE-2013-2566?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2013-2566, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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