External risk intelligence

Crypt::OpenSSL::X509 Heap Out-of-Bounds Read Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-58102

The vulnerability exists in a Perl library used for parsing X.509 certificates. While certificate parsing often occurs in internet-facing services like web servers or identity providers, the library itself is a generic component. Whether it is reachable from the public internet depends entirely on the specific application implementation and how it processes untrusted user-supplied certificates.

Out-of-bounds Read

Halo Surface Signal: 3 out of 5 — possibly public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This critical vulnerability affects Perl applications using a specific library for handling digital certificates. It allows for unauthorized reading of sensitive memory by processing specially crafted certificate data. The primary concern is to confirm if this library is used in your environment and, if so, to what extent it processes external or untrusted certificate information.

A memory reading flaw exists in certificate handling.
Confirm if this library is in use.
Assess potential exposure from certificate processing.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending a specially crafted X.509 certificate to a system that uses the vulnerable Perl library to parse certificate extensions. The library incorrectly handles the length of a certificate extension's Object Identifier (OID), leading to a heap out-of-bounds read when processing a long OID. This exposure of adjacent memory could potentially be leveraged for further compromise.

No authentication or user interaction needed.
Process a long certificate extension OID.
Heap memory disclosure, potential remote code execution.

Live Threat

Current exploitation, exposure, and threat context

When processing a long certificate extension OID, a heap out-of-bounds read could occur, potentially exposing adjacent heap memory. This could happen when the vulnerable Perl library's extension hash functions are used to parse specially crafted certificate data.

Adjacent heap memory.
Parsing malformed certificate data.
Information disclosure and denial of service.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in Crypt::OpenSSL::X509 affects systems that parse X.509 certificates, a function common in internet-facing services. Ownership will likely fall to application teams deploying these services, in coordination with infrastructure or platform teams responsible for the Perl environment, and potentially vendor management if the affected code is part of a third-party application. The immediate first step is to determine where this library is in use, assess its exposure and criticality, and identify the accountable application owner to plan remediation.

Application owners must address the issue.
Verify where the library is deployed.
Plan remediation based on exposure.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Crypt::OpenSSL::X509?

Crypt::OpenSSL::X509 is a Perl module used by developers to parse, examine, and manipulate X.509 digital certificates. It serves as a bridge to the OpenSSL library, allowing Perl-based applications to handle tasks like verifying identity or extracting metadata from security certificates used in encryption and authentication protocols.

What does CVE-2026-58102 mean for memory safety?

This vulnerability is an out-of-bounds read, classified as CWE-125. It occurs because the library miscalculates the size of certain certificate data, specifically the Object Identifier (OID). When provided with an abnormally long OID, the code reads beyond its designated memory buffer, potentially leaking sensitive data stored in the application's heap memory to the attacker.

What triggers this vulnerability in the library?

The flaw is triggered when the library processes a certificate containing a malicious, excessively long extension OID using specific hash functions like extensions() or has_extension_oid(). Importantly, using the extensions_by_name() function does not trigger this issue, as it relies on a different, static processing path that is not affected by the length miscalculation.

Is my system at risk according to Halo Surface Signal?

Halo Surface Signal notes that while this is a generic library, risk depends on whether your applications are internet-facing and process untrusted certificates. Since the vulnerability is reachable over a network, any service that uses this library to parse certificates from external, unverified sources—such as public-facing web or identity servers—faces a higher potential risk.

How should I respond to this vulnerability?

First, identify which applications in your environment utilize the Crypt::OpenSSL::X509 library. Once mapped, evaluate whether these applications parse certificate data from external or untrusted users. Prioritize remediation for services exposed to the public internet by coordinating with application owners to plan updates and limit the processing of untrusted certificate data until a fix is deployed.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.