External risk intelligence

ISO-2022 Conversion Stack Buffer Overflow in iconv

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-58082

This is a library-level buffer overflow in the iconv module. While the vulnerability allows for network-based exploitation if an application processes untrusted input, the exposure is entirely dependent on how the specific application utilizes this library. It is not an inherently reachable network service, making surface exposure possible but dependent on implementation.

Buffer Overflow

Freebsd

14.314.415.015.1

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

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability has been identified in the ISO-2022 encoding module, which could lead to a stack buffer overflow. This issue arises when converting untrusted input using the iconv function with certain affected encodings, potentially allowing for the execution of malicious code. The main concern at this stage is to confirm if this library is used and if it processes untrusted input.

Software conversion flaw may cause overflows.
Confirm if vulnerable library is used.
Assess relevance and potential exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit a vulnerability in the ISO-2022 encoding module by sending specially crafted input through an application that uses the `iconv(3)` function. This function, when converting between certain ISO-2022 encodings, can lead to a stack buffer overflow.

Untrusted input processed by `iconv(3)`.
Conversion to specific ISO-2022 encodings.
Potential for code execution or denial of service.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could impact applications using the `iconv` function to process untrusted input with specific ISO-2022 encoding conversions. When handling certain characters, a stack buffer overflow of up to four bytes may occur, potentially leading to service disruption or the execution of arbitrary code.

Application integrity and availability.
Untrusted input processed by `iconv`.
Potential for denial of service or code execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

Application owners and platform teams are likely responsible for addressing this stack buffer overflow in the ISO-2022 encoding module, especially if their applications utilize the `iconv(3)` function with untrusted input. The first practical step is to identify all instances of the affected technology, determine their reachability and business criticality, and then confirm the accountable owner before planning remediation.

Identify affected systems and owners.
Verify exposure and criticality first.
Plan remediation based on risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is iconv and the ISO-2022 module?

iconv is a standard software library used by many operating systems and applications to convert text between different character encodings. The ISO-2022 module is a specific component within this library that handles a particular set of international character standards. Software developers rely on iconv to ensure that text data is correctly interpreted when moving between different systems or language formats.

How does CVE-2026-58082 cause a buffer overflow?

This vulnerability is classified as a stack-based buffer overflow (CWE-121). It happens because the software reserves only 6 bytes for character conversion output, but certain ISO-2022 variants require up to 10 bytes. When the conversion process exceeds the reserved space, the extra data spills into adjacent memory, which can lead to unpredictable application behavior, service crashes, or unauthorized code execution.

When does this vulnerability trigger?

The issue triggers specifically when an application uses the iconv function to process untrusted input that requires conversion to or from affected ISO-2022 encodings. It does not trigger if your application only uses other encoding types or handles exclusively trusted, validated data that does not invoke the problematic ISO-2022 conversion logic.

Is my system at risk for CVE-2026-58082?

Halo Surface Signal indicates that while this is a critical vulnerability, its reachability depends entirely on your specific implementation. It is not an automatically reachable network service. You are primarily at risk if you maintain applications that use the vulnerable iconv library to process external, untrusted input. If your services do not accept or convert external data using these specific encodings, the risk is significantly lower.

What should I do first to address this?

Start by identifying all applications or services in your environment that utilize the iconv function. Once you have a list of software, determine which ones process untrusted data and confirm if they are configured to use the affected ISO-2022 encodings. Prioritize these high-risk applications for further investigation while coordinating with your development or platform teams to track updates.

References

security.freebsd.org/advisories/FreeBSD-SA-26:49.iconv.asc

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.