CVE-2013-2566

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.

Published: 2013-03-15 Last update: 2026-04-29 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2013-2566 is rated Moderate Risk (60.3/100): CVSS Medium severity, with high exploitation likelihood (EPSS 93.16%, 100th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +1.73% over the last day, indicating growing attacker interest. High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2013-2566

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-24 91.44% 93.16% +1.73%
2 2026-05-22 90.83% 91.44% +0.61%
3 2026-03-21 — 90.83% —

Full EPSS history (38 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2013-2566

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.9 3.0 MEDIUM
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 3.6 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2013-2566

OS Trackers for CVE-2013-2566

vendor priority summary link
gentoo normal CVE-2013-2566: 2 GLSA(s) (201406-19, 201504-01), 8 atom(s) (dev-libs/nspr, dev-libs/nss, …); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2013-2566
redhat medium — https://access.redhat.com/security/cve/CVE-2013-2566
ubuntu low CVE-2013-2566 low priority: Ubuntu including 3 source packages (firefox, openssl, thunderbird), 20 status rows across 8 suites (hardy, lucid, oneiric, precise, quantal, raring, saucy, upstream): released 10, ignored 9, needs-triage 1. https://ubuntu.com/security/CVE-2013-2566

Affected software / configurations for CVE-2013-2566

Vendor Product Version Raw CPE
oracle communications_application_session_controller >= 3.0.0, <= 3.9.1 cpe:2.3:a:oracle:communications_application_session_controller:*:*:*:*:*:*:*:*
oracle http_server 11.1.1.7.0 cpe:2.3:a:oracle:http_server:11.1.1.7.0:*:*:*:*:*:*:*
oracle http_server 11.1.1.9.0 cpe:2.3:a:oracle:http_server:11.1.1.9.0:*:*:*:*:*:*:*
oracle http_server 12.1.3.0.0 cpe:2.3:a:oracle:http_server:12.1.3.0.0:*:*:*:*:*:*:*
oracle http_server 12.2.1.1.0 cpe:2.3:a:oracle:http_server:12.2.1.1.0:*:*:*:*:*:*:*
oracle http_server 12.2.1.2.0 cpe:2.3:a:oracle:http_server:12.2.1.2.0:*:*:*:*:*:*:*
oracle integrated_lights_out_manager_firmware >= 3.0.0, <= 3.2.11 cpe:2.3:o:oracle:integrated_lights_out_manager_firmware:*:*:*:*:*:*:*:*
oracle integrated_lights_out_manager_firmware >= 4.0.0, <= 4.0.4 cpe:2.3:o:oracle:integrated_lights_out_manager_firmware:*:*:*:*:*:*:*:*
fujitsu sparc_enterprise_m3000_firmware >= xcp, < xcp_1121 cpe:2.3:o:fujitsu:sparc_enterprise_m3000_firmware:*:*:*:*:*:*:*:*
fujitsu sparc_enterprise_m4000_firmware >= xcp, < xcp_1121 cpe:2.3:o:fujitsu:sparc_enterprise_m4000_firmware:*:*:*:*:*:*:*:*
fujitsu sparc_enterprise_m5000_firmware >= xcp, < xcp_1121 cpe:2.3:o:fujitsu:sparc_enterprise_m5000_firmware:*:*:*:*:*:*:*:*
fujitsu sparc_enterprise_m8000_firmware >= xcp, < xcp_1121 cpe:2.3:o:fujitsu:sparc_enterprise_m8000_firmware:*:*:*:*:*:*:*:*
fujitsu sparc_enterprise_m9000_firmware >= xcp, < xcp_1121 cpe:2.3:o:fujitsu:sparc_enterprise_m9000_firmware:*:*:*:*:*:*:*:*
fujitsu m10-1_firmware >= xcp, < xcp2280 cpe:2.3:o:fujitsu:m10-1_firmware:*:*:*:*:*:*:*:*
fujitsu m10-4_firmware >= xcp, < xcp2280 cpe:2.3:o:fujitsu:m10-4_firmware:*:*:*:*:*:*:*:*
fujitsu m10-4s_firmware >= xcp, < xcp2280 cpe:2.3:o:fujitsu:m10-4s_firmware:*:*:*:*:*:*:*:*
canonical ubuntu_linux 12.04 cpe:2.3:o:canonical:ubuntu_linux:12.04:*:*:*:esm:*:*:*
canonical ubuntu_linux 12.10 cpe:2.3:o:canonical:ubuntu_linux:12.10:*:*:*:*:*:*:*
canonical ubuntu_linux 13.04 cpe:2.3:o:canonical:ubuntu_linux:13.04:*:*:*:*:*:*:*
canonical ubuntu_linux 13.10 cpe:2.3:o:canonical:ubuntu_linux:13.10:*:*:*:*:*:*:*
mozilla firefox < 17.0.11 cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
mozilla firefox < 25.0.1 cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
mozilla firefox >= 24.1.0, < 24.1.1 cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
mozilla seamonkey < 2.22.1 cpe:2.3:a:mozilla:seamonkey:*:*:*:*:*:*:*:*
mozilla thunderbird < 24.1.1 cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
mozilla thunderbird_esr < 17.0.11 cpe:2.3:a:mozilla:thunderbird_esr:*:*:*:*:*:*:*:*

References for CVE-2013-2566

URL Tags
http://blog.cryptographyengineering.com/2013/03/attack-of-week-rc4-is-kind-of-broken-in.html Third Party Advisory
http://cr.yp.to/talks/2013.03.12/slides.pdf Third Party Advisory
http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10705 Third Party Advisory
http://marc.info/?l=bugtraq&m=143039468003789&w=2 Issue Tracking Third Party Advisory
http://my.opera.com/securitygroup/blog/2013/03/20/on-the-precariousness-of-rc4 Third Party Advisory
http://security.gentoo.org/glsa/glsa-201406-19.xml Third Party Advisory
http://www.isg.rhul.ac.uk/tls/ Third Party Advisory
http://www.mozilla.org/security/announce/2013/mfsa2013-103.html Third Party Advisory
http://www.opera.com/docs/changelogs/unified/1215/ Third Party Advisory
http://www.opera.com/security/advisory/1046 Third Party Advisory
http://www.oracle.com/technetwork/security-advisory/cpuapr2016v3-2985753.html Third Party Advisory
http://www.oracle.com/technetwork/security-advisory/cpujan2018-3236628.html Third Party Advisory
http://www.oracle.com/technetwork/security-advisory/cpujul2016-2881720.html Third Party Advisory
http://www.oracle.com/technetwork/security-advisory/cpuoct2016-2881722.html Third Party Advisory
http://www.oracle.com/technetwork/security-advisory/cpuoct2017-3236626.html Third Party Advisory
http://www.securityfocus.com/bid/58796 Third Party Advisory VDB Entry
http://www.ubuntu.com/usn/USN-2031-1 Third Party Advisory
http://www.ubuntu.com/usn/USN-2032-1 Third Party Advisory
https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05289935 Third Party Advisory
https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05336888 Third Party Advisory
https://security.gentoo.org/glsa/201504-01 Third Party Advisory
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