External risk intelligence

Text::CSV_XS Parse Malformed UTF-8 Byte Injection

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-110759

Text::CSV_XS is a library for parsing CSV files, typically integrated into applications to process local or uploaded data. It is not a network-facing service, appliance, or gateway itself. Exposure is dependent on how a developer implements the library, making public-internet-facing, direct reachability unlikely.

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

This advisory concerns a vulnerability in a widely used Perl module for processing CSV files. The issue arises when parsing specific file endings, potentially leading to the introduction of unexpected bytes into data processing, which could have implications for data integrity and application behavior. The main concern is confirming relevance and exposure.

Unexpected data may enter processing.
Affects CSV parsing in many applications.
Confirm if this library is in use.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted CSV data to an application that uses a vulnerable version of the Text::CSV_XS library. If the data ends with an empty field followed by a carriage return (CR), the library might incorrectly parse it, introducing a non-input byte (0xFF) into the processed data. This could lead to the application processing unexpected and potentially malformed data.

Requires specially crafted CSV data.
Vulnerable CSV parsing in the library.
Application may process unexpected data.

Live Threat

Current exploitation, exposure, and threat context

When parsing CSV data, an unexpected byte could be introduced into a field, potentially affecting how applications interpret or process that data. This could occur when input lines end with a carriage return (CR) and the last field is empty.

System data could be altered.
Malformed data could be parsed.
Application logic may fail.

Operational Fix

Recommended remediation, mitigation, and detection steps

Ownership for issues involving Text::CSV_XS typically falls to application owners who integrate the library, as its exposure is determined by how it's used within a given application. The first practical step is to identify applications utilizing this library, determine their business criticality and exposure, and then locate the accountable development or platform team. Planning remediation should be based on the assessed risk and confirmed ownership.

Application owners should track library usage.
Verify applications parsing external CSV data.
Plan remediation based on risk assessment.

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 Text::CSV_XS and how is it used?

Text::CSV_XS is a Perl module designed for high-performance parsing and manipulation of CSV files. Developers commonly integrate this library into software applications to read, write, and process data structures formatted as comma-separated values, often bridging the gap between flat files and internal application logic.

How does CVE-2026-110759 cause data issues?

This vulnerability is classified as CWE-1286, which relates to the improper validation of input data. The library incorrectly interprets specific end-of-line sequences, such as an empty field followed by a carriage return. This causes the parser to inject a 0xFF byte—which is absent from the original source—into the output, potentially resulting in malformed strings or incorrect data handling.

Does any CSV file trigger this parsing error?

No. The flaw is not triggered by standard, well-formatted CSV data. It specifically occurs only when a line ends with an empty field followed immediately by a lone carriage return. If the last field contains data or follows standard line-ending conventions, the parser does not generate the unexpected byte.

Is my software vulnerable to CVE-2026-110759?

According to Halo Surface Signal, this is unlikely. Because the library is a background component rather than a standalone network service, your risk depends entirely on whether your application accepts and parses untrusted CSV files from external sources. If your software only processes internal or trusted data, the likelihood of an attacker reaching this code path is very low.

What is the first step to address this risk?

Begin by auditing your software inventory to locate applications that rely on the Text::CSV_XS library. Once identified, evaluate whether these applications process CSV data from untrusted users or external origins. Collaborate with the development teams responsible for those applications to verify the current library version and prioritize updates accordingly.

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.