CVE-2016-6309

What it is

statem/statem.c in OpenSSL 1.1.0a does not consider memory-block movement after a realloc call, which allows remote attackers to cause a denial of service (use-after-free) or possibly execute arbitrary code via a crafted TLS session.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

70.2% chance of exploitation in the next 30 days (EPSS). Higher than most.

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2016-07-26 00:00 UTC ReservedThe CVE id was reserved by its CNA
2. 2016-09-26 19:59 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-06-17 00:50 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 70.2% in the next 30 days (EPSS).
• Severity: 9.8 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.
• It meets the bar for Drop everything: critical, and exploited or very likely to be.

Details

Published

2016-09-26 19:59 UTC

Last modified

2026-06-17 00:50 UTC

Exploit probability

70.2% · EPSS, next 30 days

Weakness

CWE-416 · Use after free

Record status

Modified

Affected

• OpenSSL 1.1.0a

Attack profile CVSS 3.0 · 9.8

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2016-6309.md and follow it. Check whether this project is affected by CVE-2016-6309. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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