CVE-2016-2181

What it is

The Anti-Replay feature in the DTLS implementation in OpenSSL before 1.1.0 mishandles early use of a new epoch number in conjunction with a large sequence number, which allows remote attackers to cause a denial of service (false-positive packet drops) via spoofed DTLS records, related to rec_layer_d1.c and ssl3_record.c.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Exploit odds

22.6% chance of exploitation in the next 30 days (EPSS). Higher than most.

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2016-09-16 05:59 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 00:43 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 22.6% in the next 30 days (EPSS).
• Severity: 7.5 HIGH (CVSS).
• Fix: none linked yet, which raises it.

Details

Published

2016-09-16 05:59 UTC

Last modified

2026-06-17 00:43 UTC

Exploit probability

22.6% · EPSS, next 30 days

Weakness

CWE-189

Record status

Modified

Affected

• OpenSSL 1.0.1
• OpenSSL 1.0.1a
• OpenSSL 1.0.1b
• OpenSSL 1.0.1c
• OpenSSL 1.0.1d
• OpenSSL 1.0.1e
• OpenSSL 1.0.1f
• OpenSSL 1.0.1g

Attack profile CVSS 3.0 · 7.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

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.

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