External risk intelligence

ExtUtils::Typemaps::STL::String Argument Stringification Flaw

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-107373

This vulnerability exists within a Perl module used for C++ typemapping during the build or compilation process. It is a developer-centric tool used for software development and integration, not an internet-facing service, network gateway, or deployed application component, making public internet exposure via this mechanism extremely unlikely in real-world deployments.

Out-of-bounds Read

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability has been identified in a Perl module used for C++ type mapping. This issue could lead to program instability or crashes if certain conditions are met during the build process. The main concern is confirming whether this specific module is in use within our development or build environments.

Perl module may crash under specific conditions.
Confirm relevance and exposure in development.
Understand impact and verify usage internally.

Attack Path

How an attacker could exploit the issue

An attacker could trigger this vulnerability by providing unexpected data types to a Perl module that handles C++ typemapping. This module, intended for use during software development, may incorrectly process non-string arguments, leading to program instability.

Entry condition: Malformed data during module processing.
Trigger point: Incorrectly evaluated C++ argument.
Resulting risk: Program may crash or become unstable.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could cause a Perl application to crash or behave unexpectedly when the `ExtUtils::Typemaps::STL::String` module is used to convert non-string data types to C++ strings. This might occur during the build or compilation process if the typemap incorrectly attempts to determine the length of non-string arguments, potentially leading to denial of service.

Application stability.
Invalid argument types may cause crashes.
Service may become unavailable.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability is in a Perl module used during the build or compilation process, making its direct exposure unlikely in most production environments. If this module is integrated into build pipelines or development tools, the application or platform engineering teams would likely be responsible for assessing its impact and managing any necessary updates. The first practical step is to determine if and where this module is used in your development lifecycle, confirm its reachability within your build or development infrastructure, and identify the accountable team for managing developer tooling.

Platform/DevOps teams own the issue.
Verify usage in build/dev environments.
Update build tools or modules.

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 the ExtUtils::Typemaps::STL::String module?

This Perl module is a developer-centric utility used to help bridge Perl and C++ code. Specifically, it handles 'typemapping,' which instructs the computer on how to convert data structures between the two languages during software compilation or build processes. It is typically found in development environments where programmers are integrating Perl scripts with C++ libraries.

Why is CVE-2026-107373 considered a CWE-125 weakness?

This CVE is categorized as an Out-of-Bounds Read (CWE-125). It occurs because the module attempts to read the length of an argument before confirming if the data is actually a string. If the provided data is a number or a reference instead of a string, the software tries to access memory that doesn't belong to it, potentially causing the program to abort or crash.

How can an attacker trigger this vulnerability?

The flaw is triggered when the module receives non-string input, such as an integer or a reference, while attempting to process a C++ typemap. Because the C++ compiler's evaluation order is undefined, the program may incorrectly calculate the data length. Providing a valid string as the input does not trigger the bug, as the error specifically arises from the mishandling of unexpected, non-string data types.

Is my production server at risk from this CVE?

According to Halo Surface Signal, this vulnerability is very unlikely to be exploited via the internet. Because the module is a tool for developers during the software build process rather than an internet-facing application component or network service, it is not typically exposed to external network traffic in standard production deployments.

What should I do if my team uses this module?

First, identify where this module exists within your build pipelines or internal development infrastructure. You do not need to treat this as an immediate internet-facing threat. Instead, work with your platform engineering or DevOps teams to verify if your current version is affected and plan for an update to a patched version of the module as part of your standard maintenance lifecycle.

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.