CVE-2021-3449

What it is

An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello omits the signature_algorithms extension (where it was present in the initial ClientHello), but includes a signature_algorithms_cert extension then a NULL pointer dereference will result, leading to a crash and a denial of service attack. A server is only vulnerable if it has TLSv1.2 and renegotiation enabled (which is the default configuration). OpenSSL TLS clients are not impacted by this issue. All OpenSSL 1.1.1 versions are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j).

At a glance

Exploitability

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

Exploit odds

63.5% 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. 2021-03-25 15:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-08 22:17 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 63.5% in the next 30 days (EPSS).
• Severity: 5.9 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-03-25 15:15 UTC

Last modified

2026-10-08 22:17 UTC

Exploit probability

63.5% · EPSS, next 30 days

Weakness

CWE-476 · NULL pointer dereference

Record status

Modified

Affected

• OpenSSL < 1.1.1k
• Debian Linux 9.0
• Debian Linux 10.0
• Freebsd 12.2
• Netapp Active Iq Unified Manager
• Netapp Cloud Volumes Ontap Mediator
• Netapp e-series Performance Analyzer
• Netapp Oncommand Insight

Attack profile CVSS 3.1 · 5.9

Attack vector

Network

Complexity

High

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.

Read https://cve-list.com/agent/cve/CVE-2021-3449.md and follow it. Check whether this project is affected by CVE-2021-3449. 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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