CVE-2017-3737

What it is

OpenSSL 1.0.2 (starting from version 1.0.2b) introduced an "error state" mechanism. The intent was that if a fatal error occurred during a handshake then OpenSSL would move into the error state and would immediately fail if you attempted to continue the handshake. This works as designed for the explicit handshake functions (SSL_do_handshake(), SSL_accept() and SSL_connect()), however due to a bug it does not work correctly if SSL_read() or SSL_write() is called directly. In that scenario, if the handshake fails then a fatal error will be returned in the initial function call. If SSL_read()/SSL_write() is subsequently called by the application for the same SSL object then it will succeed and the data is passed without being decrypted/encrypted directly from the SSL/TLS record layer. In order to exploit this issue an application bug would have to be present that resulted in a call to SSL_read()/SSL_write() being issued after having already received a fatal error. OpenSSL version 1.0.2b-1.0.2m are affected. Fixed in OpenSSL 1.0.2n. OpenSSL 1.1.0 is not affected.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure.

Exploit odds

78.7% 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. 2017-12-07 16:29 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 01:18 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 78.7% in the next 30 days (EPSS).
• Severity: 5.9 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2017-12-07 16:29 UTC

Last modified

2026-06-17 01:18 UTC

Exploit probability

78.7% · EPSS, next 30 days

Weakness

CWE-125 · Out-of-bounds read

Record status

Modified

Affected

• OpenSSL 1.0.2b
• OpenSSL 1.0.2c
• OpenSSL 1.0.2d
• OpenSSL 1.0.2e
• OpenSSL 1.0.2f
• OpenSSL 1.0.2g
• OpenSSL 1.0.2h
• OpenSSL 1.0.2i

Attack profile CVSS 3.0 · 5.9

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

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-2017-3737.md and follow it. Check whether this project is affected by CVE-2017-3737. 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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