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CVE-2016-6309

64
FAUCET Score

CVE-2016-6309 is a critical use-after-free vulnerability in OpenSSL 1.1.0a, specifically within the statem/statem.c component. This flaw arises because the software fails to account for memory block relocation after a realloc call, allowing remote attackers to trigger a denial of service or potentially execute arbitrary code through a specially crafted TLS session. With a CVSS score of 9.8 (Critical), it presents a severe risk due to its network-based attack vector, low attack complexity, and high impact on confidentiality, integrity, and availability. Despite its high severity and significant media coverage, there is no evidence of active exploitation, and public exploit code (Metasploit, Nuclei, ExploitDB) is currently unavailable.

Impacted Technologies

VendorProductVersion(s)CPE
1.1.0aCPE matchmatch criteria
cpe:2.3:a:openssl:openssl:1.1.0a:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

9.8CRITICAL

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
70.22%
Probability of exploitation in next 30 days
EPSS Percentile
99.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.7022 is in the 98th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

redhatCVE-2016-6309Critical

openssl: Use After Free for large message sizes

Sep 26, 2016

References

kb.juniper.net / InfoCenter/index
bto.bluecoat.com / security-advisory/sa132
git.openssl.org
support.hpe.com / hpsc/doc/public/display
openssl.org / news/secadv/20160926.txt
Vendor Advisory
tenable.com / security/tns-2016-16
tenable.com / security/tns-2016-20
www-01.ibm.com / support/docview.wss
oracle.com / technetwork/security-advisory/cpuapr2018-3678067.html
oracle.com / technetwork/security-advisory/cpujan2018-3236628.html
oracle.com / technetwork/security-advisory/cpujul2017-3236622.html
oracle.com / technetwork/security-advisory/cpuoct2016-2881722.html
securityfocus.com / bid/93177
securitytracker.com / id/1036885