External risk intelligence

HTTP::Daemon Perl Module OS Command Injection

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-8450

HTTP::Daemon is a library specifically designed to build web servers and HTTP-based services in Perl. As a component used to implement internet-facing web applications and HTTP services, the vulnerable function is exposed to input typically provided by network clients in public-facing deployment patterns.

OS Command Injection

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This critical vulnerability impacts Perl's HTTP::Daemon library, affecting how it handles file operations. It could allow attackers to execute commands on the server or manipulate files, potentially compromising system integrity. The main concern is confirming relevance and exposure to this component.

Allows command execution or file tampering.
Critical flaw in a web service component.
Confirm if this library is in use.

Attack Path

How an attacker could exploit the issue

An attacker can exploit this vulnerability by sending specially crafted input to a web service that uses the vulnerable component. This input can trick the service into executing arbitrary operating system commands on the server, potentially allowing the attacker to steal sensitive data or modify files.

Vulnerable component exposed to the network.
Sending malicious input to the `send_file()` function.
Remote command execution and unauthorized file access.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an attacker to inject and execute arbitrary operating system commands on the server running the affected Perl daemon. This could occur when untrusted input is passed to the `send_file()` function, potentially leading to the compromise of the daemon's process, or the leakage of sensitive data through the HTTP response. The vulnerability also allows for the creation or modification of files on the server at attacker-specified locations.

OS commands and server files at risk.
Untrusted input to `send_file()` function.
Remote command execution and file manipulation.

Operational Fix

Recommended remediation, mitigation, and detection steps

Identifying and remediating OS command injection vulnerabilities in HTTP::Daemon requires a coordinated effort, likely involving Perl application owners, platform teams managing the Perl runtime, and security teams to assess exposure. The immediate first step is to locate all instances of the affected HTTP::Daemon library within your environment, determine their reachability from external networks, and assess their business criticality to prioritize remediation actions.

Application owners must confirm usage and criticality.
Verify network exposure and business impact.
Plan coordinated updates or mitigations.

Supplementary metadata

CVSS vector

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Frequently asked questions

What is the HTTP::Daemon module?

HTTP::Daemon is a library used in the Perl programming language to create lightweight web servers and facilitate HTTP-based network communication. Developers often integrate it into applications to handle incoming web requests or to build custom services that communicate via the HTTP protocol. It acts as the foundation for the server-side logic in these specific Perl-based web services.

How does CVE-2026-8450 enable OS command injection?

The vulnerability stems from the use of Perl's two-argument open() function within the send_file() method. Because this function treats certain characters as instructions for pipes or file manipulation, an attacker can supply specially crafted strings. This weakness, classified as CWE-78 (OS Command Injection) and CWE-73 (External Control of File Name), allows the application to mistakenly execute operating system commands or perform unintended file operations.

What triggers the vulnerability in send_file()?

The flaw is triggered when untrusted user input is passed directly as an argument to the send_file() function. If the input is not sanitized or validated, the daemon interprets it as a command or file path. It is important to note that if the application code only passes hardcoded, trusted file paths that cannot be influenced by user input, the application will not be susceptible to this specific injection path.

Is my system at risk for CVE-2026-8450?

Halo Surface Signal indicates that because HTTP::Daemon is typically used to build services accessible over a network, any application using an affected version that accepts input from internet-facing clients is at higher risk. You should evaluate whether your Perl-based services are exposed to untrusted network traffic, as this increases the likelihood that an attacker could reach the vulnerable send_file() function.

What should I do to address this vulnerability?

The primary step is to identify all applications in your environment that utilize versions of HTTP::Daemon earlier than 6.17. Once identified, coordinate with your application teams to update the library to a patched version. Prioritize systems that are reachable from the internet, as these represent the most immediate points of concern for potential exploitation.

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.