CVE-2026-5393Network attack vector

Out-of-bounds read via unchecked signature length

Published Apr 9, 2026 · Updated Apr 9, 2026

Out-of-bounds read in wolfSSL before 5.9.1 allows remote attackers to trigger invalid memory access via crafted CertificateVerify data. DoTls13CertificateVerify advances past the first dual-algorithm signature and reads the next two-byte length without first confirming that those bytes remain. Only experimental builds compiled with both --enable-experimental and --enable-dual-alg-certs are exposed; wolfSSL has not published a concrete consequence beyond the read.

CVSS severity6.3
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Out-of-bounds read in wolfSSL before 5.9.1 allows remote attackers to trigger invalid memory access via crafted CertificateVerify data. DoTls13CertificateVerify advances past the first dual-algorithm signature and reads the next two-byte length without first confirming that those bytes remain. Only experimental builds compiled with both --enable-experimental and --enable-dual-alg-certs are exposed; wolfSSL has not published a concrete consequence beyond the read.

The record

CVE
CVE-2026-5393
Published
Apr 9, 2026
Updated
Apr 9, 2026
Vendor
wolfSSL
Product
wolfSSL
Classifications
CWE-125
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <5.9.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

wolfSSL · wolfSSLversion=0 <5.9.1

Published CVSS scores

6.3wolfSSL Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo