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PYSEC-2026-575

CriticalCVSS 9.3 / 10
Published Jun 29, 2026·Last modified Jun 29, 2026
Affected Components(0)

No affected components available

Description

A vulnerability in the handling of verify_mode = CERT_REQUIRED in the wolfssl Python package (wolfssl-py) causes client certificate requirements to not be fully enforced. 

Because the WOLFSSL_VERIFY_FAIL_IF_NO_PEER_CERT flag was not included, the behavior effectively matched CERT_OPTIONAL: a peer certificate was verified if presented, but connections were incorrectly authenticated when no client certificate was provided. 

This results in improper authentication, allowing attackers to bypass mutual TLS (mTLS) client authentication by omitting a client certificate during the TLS handshake. 

The issue affects versions up to and including 5.8.2.

Risk Scores
Base Score
9.3

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.

Threat Intelligence
8.0

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.27%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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