CVE-2026-55962

6.5

MEDIUM CVSS 3.1

TLS 1.3 post-handshake authentication: server accepts Finished without client Certificate/CertificateVerify

Overview

Description

TLS 1.3 post-handshake authentication (PHA) issue where a server could accept a client's Finished message without the client having sent a Certificate and CertificateVerify. The post-handshake-auth exemption that allows an empty/absent peer certificate was only intended for the initial handshake, but it was also being applied while a post-handshake CertificateRequest was still outstanding. The check is now scoped to the initial handshake only: on the server, once a post-handshake CertificateRequest has been sent (certReqCtx is set), a peer certificate and a valid CertificateVerify are required again before the Finished is accepted, with empty-certificate handling following the configured verify mode (FAIL_IF_NO_PEER_CERT) just as during first-handshake client authentication. Only affects TLS 1.3 servers built with post-handshake authentication support (WOLFSSL_POST_HANDSHAKE_AUTH / --enable-postauth, included in --enable-all) that enable WOLFSSL_VERIFY_POST_HANDSHAKE and request a client certificate after the handshake via wolfSSL_request_certificate(). Clients, and servers that do not use post-handshake authentication, are unaffected.

Details

INFO

Published Date :

June 25, 2026, 10:17 p.m.

Last Modified :

June 27, 2026, 7:57 p.m.

Remotely Exploit :

Yes !

Source :

[email protected]

Impact

Affected Products

The following products are affected by CVE-2026-55962 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID	Vendor	Product	Action
1	Wolfssl	wolfssl

: Total Affected Vendor : 1 | Products : 1

Scoring

CVSS Scores

The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.

Version	Severity	Source
CVSS		134c704f-9b21-4f2e-91b3-4a467353bcc0
CVSS 3.1	MEDIUM	[email protected]
CVSS 4.0	MEDIUM	50d2cd11-d01a-48ed-9441-5bfce9d63b27
CVSS 4.0	MEDIUM	[email protected]

Solution

Update TLS server to restrict post-handshake authentication exemptions to the initial handshake.

Update TLS server software to the latest version.
Configure TLS server to properly handle client certificates.
Ensure post-handshake authentication is correctly scoped.

Public PoC/Exploit Available at Github

CVE-2026-55962 has a 3 public PoC/Exploit available at Github. Go to the Public Exploits tab to see the list.

References

References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-55962.

URL	Resource
https://github.com/wolfSSL/wolfssl/pull/10702	Issue Tracking Patch
https://www.wolfssl.com/docs/security-vulnerabilities/	Vendor Advisory

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-55962 is associated with the following CWEs:

CWE-287: Improper Authentication

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-55962 weaknesses.

CAPEC-22: Exploiting Trust in Client Exploiting Trust in Client CAPEC-57: Utilizing REST's Trust in the System Resource to Obtain Sensitive Data Utilizing REST's Trust in the System Resource to Obtain Sensitive Data CAPEC-94: Adversary in the Middle (AiTM) Adversary in the Middle (AiTM) CAPEC-114: Authentication Abuse Authentication Abuse CAPEC-115: Authentication Bypass Authentication Bypass CAPEC-151: Identity Spoofing Identity Spoofing CAPEC-194: Fake the Source of Data Fake the Source of Data CAPEC-593: Session Hijacking Session Hijacking CAPEC-633: Token Impersonation Token Impersonation CAPEC-650: Upload a Web Shell to a Web Server Upload a Web Shell to a Web Server

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

CodeLinaro-mirror/qrdk_wolfssl

None

CMake C++ Shell C Makefile Batchfile Linker Script Perl FreeMarker Objective-C

Updated: 2 weeks, 1 day ago

0 stars 0 fork 0 watcher

Born at : April 28, 2026, 8:45 p.m. This repo has been linked 33 different CVEs too.

w4zu/Debian_security

DSA and DLA for Debian last 14 days

Python

Updated: 1 week, 3 days ago

2 stars 1 fork 1 watcher

Born at : Feb. 12, 2025, 2:08 p.m. This repo has been linked 584 different CVEs too.

wolfSSL/wolfssl

The wolfSSL library is a small, fast, portable implementation of TLS/SSL for embedded devices to the cloud. wolfSSL supports up to TLS 1.3 and DTLS 1.3! Update to wolfSSL 5.9.1 for the latest CVE fixes.

ssl tls cryptography security openssl tls13 dtls https fips cryptography-api embedded-systems encryption iot trusted-execution-environment openssl-alternative c-library wolfssl cipher-suites openssl-api sniffer

C Shell Makefile Tcl Assembly C++ XS Perl C# M4

Updated: 1 week, 3 days ago

2874 stars 976 fork 976 watcher

Born at : Jan. 7, 2015, 6:50 p.m. This repo has been linked 33 different CVEs too.

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-55962 vulnerability anywhere in the article.

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2026-55962 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

Initial Analysis by [email protected]

Jun. 27, 2026

Action	Type	New Value
Added	CVSS V3.1	AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Added	CWE	NVD-CWE-noinfo
Added	CPE Configuration	OR cpe:2.3:a:wolfssl:wolfssl::::::::* versions from (including) 5.5.4 up to (excluding) 5.9.2
Added	Reference Type	wolfSSL Inc.: https://github.com/wolfSSL/wolfssl/pull/10702 Types: Issue Tracking, Patch
Added	Reference Type	wolfSSL Inc.: https://www.wolfssl.com/docs/security-vulnerabilities/ Types: Vendor Advisory

CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

Jun. 26, 2026

Action	Type	Old Value	New Value
Added	SSVC		{'id': 'CVE-2026-55962', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-26T10:30:28.816026Z'}

New CVE Received by [email protected]

Jun. 25, 2026

Action	Type	New Value
Added	Affected	[{'vendor': 'wolfSSL', 'product': 'wolfSSL', 'versions': [{'status': 'affected', 'version': '5.5.4', 'versionType': 'semver', 'lessThanOrEqual': '5.9.1'}], 'collectionURL': 'https://github.com/wolfSSL/wolfssl', 'defaultStatus': 'unaffected'}]
Added	Description	TLS 1.3 post-handshake authentication (PHA) issue where a server could accept a client's Finished message without the client having sent a Certificate and CertificateVerify. The post-handshake-auth exemption that allows an empty/absent peer certificate was only intended for the initial handshake, but it was also being applied while a post-handshake CertificateRequest was still outstanding. The check is now scoped to the initial handshake only: on the server, once a post-handshake CertificateRequest has been sent (certReqCtx is set), a peer certificate and a valid CertificateVerify are required again before the Finished is accepted, with empty-certificate handling following the configured verify mode (FAIL_IF_NO_PEER_CERT) just as during first-handshake client authentication. Only affects TLS 1.3 servers built with post-handshake authentication support (WOLFSSL_POST_HANDSHAKE_AUTH / --enable-postauth, included in --enable-all) that enable WOLFSSL_VERIFY_POST_HANDSHAKE and request a client certificate after the handshake via wolfSSL_request_certificate(). Clients, and servers that do not use post-handshake authentication, are unaffected.
Added	CVSS V4.0	AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Added	CWE	CWE-287
Added	Reference	https://github.com/wolfSSL/wolfssl/pull/10702
Added	Reference	https://www.wolfssl.com/docs/security-vulnerabilities/

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.