External risk intelligence

Perl Socket Out-of-Bounds Heap Read Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-12087

A heap read vulnerability in Perl's Socket component could allow attackers to disclose adjacent memory. The issue stems from improper length checking during IP multicast source address packing, potentially leading to information disclosure.

2Halo Surface Signal

Out-of-bounds Read

External exposure likelihood

Halo Surface Signal score for CVE-2026-12087

The vulnerability exists in a Perl library used for low-level socket operations. While the library is network-accessible, it is a developer-focused utility library rather than an internet-facing service, appliance, or application. Direct exposure to the public internet is uncommon as it typically resides within the internal logic of custom applications.

PCI scan relevance

PCI Relevance for CVE-2026-12087

Yes

CVE-2026-12087 — Halo PCI Relevance: Yes. Under typical PCI ASV external scan criteria, this issue may be flagged for scan prioritization.

This vulnerability in Perl's Socket module allows an out-of-bounds heap read and is rated critical. It could impact systems processing network data.

Scan-prioritization guidance only—not a PCI DSS certification or ASV attestation.

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability has been identified in a Perl library impacting socket operations. This issue, a heap read, could allow unauthorized access to adjacent memory. The primary concern is to confirm if this library is in use and assess potential exposure.

Memory reading flaw in Perl socket library.
Confirms use and exposure to manage risk.
Understand impact on internal application logic.

Attack Path

How an attacker could exploit the issue

An attacker could reach this vulnerability by sending specially crafted network data to a Perl application that uses a vulnerable version of the Socket library. The `pack_ip_mreq_source()` function within the library incorrectly handles the length of source address data. This could lead to an out-of-bounds heap read, potentially exposing sensitive information from the application's memory.

Network exposure is required.
Triggered by malformed source address data.
Risk of sensitive memory disclosure.

Live Threat

Current exploitation, exposure, and threat context

The vulnerability in the Perl Socket library could allow an attacker to read adjacent memory when a specially crafted source argument is provided to the `pack_ip_mreq_source()` function. This occurs because the length check for the source argument is bypassed due to how it interacts with the preceding `multiaddr` argument.

Unintended memory reads.
Heap memory exposure.
Potential denial of service.

Operational Fix

Recommended remediation, mitigation, and detection steps

The Perl Socket library's heap read vulnerability necessitates an immediate inventory of all applications and systems utilizing this library, with a focus on those exposed externally or handling sensitive data. Application owners and platform teams should collaborate to confirm the presence of the affected library, assess business criticality and reachability, and then prioritize remediation efforts. Vendor management may be involved if the library is part of a third-party product.

Application owners should own this issue.
Verify external or sensitive data exposure.
Plan remediation based on assessed risk.

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.

Free EASM Trial See How Signal Works

Frequently asked questions

What is the Socket module for Perl?

The Socket module is a fundamental component of the Perl programming language that provides the necessary tools for networking. It allows developers to create and manage network sockets—the low-level endpoints used to send and receive data across a network—enabling applications to perform tasks like connecting to web services or listening for incoming data traffic.

What does CVE-2026-12087 mean?

This vulnerability is an out-of-bounds heap read, categorized under CWE-125 (Out-of-bounds Read) and CWE-805 (Buffer Access with Incorrect Length Value). It occurs when the code incorrectly validates the length of data being processed. Instead of reading only the intended amount of data, the system inadvertently reads extra bytes from adjacent memory, which could potentially leak sensitive information stored in the heap.

How is this vulnerability triggered?

The issue is triggered when the pack_ip_mreq_source() function is called with a source address argument that is shorter than four bytes. If the provided input is too small, the internal check fails to prevent a fixed-size copy operation. Conversely, providing a source address that meets the full four-byte requirement ensures the length check operates as expected, preventing the out-of-bounds read.

Should I be concerned about CVE-2026-12087?

According to Halo Surface Signal, this vulnerability is unlikely to be a direct target because the Socket module is a developer utility library, not an internet-facing application or service. It generally operates within the internal logic of custom-built software. Unless your specific application exposes this function to untrusted input from the public internet, the risk is typically contained.

What are the first steps to address this issue?

To resolve the vulnerability, you should update the Socket module to version 2.041 or later. Since this is a library-level fix, you will need to identify which applications in your environment utilize the Perl Socket library and ensure they are updated to the patched version. Review your software inventory to confirm where this dependency is used in your custom codebases.

References

Written by Nicholas Merritt

External-surface CVE analysis and Halo Surface Signal prioritization for Halo Threat Intelligence.