External risk intelligence

RTKLIB Type-1033 Message Out-of-Bounds Write Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-56786

RTKLIB is a software library used for processing GNSS data. While it can ingest network-based NTRIP streams, these streams are typically specialized data feeds used in scientific, surveying, or industrial contexts rather than common, wide-scale internet-facing web or gateway services. Exposure depends heavily on the specific implementation and network configuration of the GNSS receiver or server.

Out-of-bounds Write

Rtklib

2.4.3 and earlier

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

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability has been identified in RTKLIB software, which is used for processing Global Navigation Satellite System (GNSS) data. This flaw could allow an attacker to execute arbitrary code or cause a denial of service by sending a specially crafted message over a network connection. The main concern is to confirm if this technology is used within our environment and to what extent it may be exposed.

Software flaw allows remote code execution or denial of service.
Confirm if this specific data processing technology is in use.
Assess relevance and potential exposure in our environment.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending a specially crafted correction stream over NTRIP or a serial connection to a vulnerable RTKLIB instance. This crafted message, designed to trigger an out-of-bounds write, could corrupt critical data structures, potentially leading to code execution or a service disruption.

Entry condition: Unauthenticated network access to correction stream.
Trigger point: Crafting a type-1033 message with CRC.
Resulting risk: Arbitrary code execution or denial of service.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could affect systems processing GNSS data streams, such as those used in surveying or industrial applications. An attacker could send specially crafted data over an NTRIP or serial connection to trigger an out-of-bounds write, potentially leading to system compromise.

GNSS data processing systems.
Corrupted data streams over network.
Arbitrary code execution or DoS.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in RTKLIB affects software that processes GNSS correction streams. Owners of systems utilizing RTKLIB, particularly those ingesting NTRIP or RTCM3 data, should identify these deployments, assess their business criticality and external reachability, and determine the accountable application or infrastructure team for remediation planning.

Identify RTKLIB deployments and assess exposure.
Confirm accountable application or infrastructure owner.
Plan risk-based remediation actions.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is RTKLIB and how is it used?

RTKLIB is an open-source software library designed for standard and high-precision positioning with Global Navigation Satellite System (GNSS) data. It is widely employed by researchers, surveyors, and industrial engineers to process signals from satellite constellations like GPS, Galileo, and GLONASS. The software frequently ingests real-time correction data, such as RTCM3 streams via NTRIP protocols, to calculate accurate geographic coordinates for specialized equipment and infrastructure.

What does CVE-2026-56786 mean for data security?

This vulnerability is an out-of-bounds write flaw, classified as CWE-787. In plain terms, the software fails to verify the size of incoming data before writing it to a specific memory area. Because the code attempts to save a message larger than the designated space, it overwrites adjacent memory. This corruption can lead to unpredictable behavior, including the ability for an attacker to force the software to execute unauthorized commands or cause the system to crash entirely.

How can an attacker trigger this RTKLIB vulnerability?

An attacker triggers the bug by sending a malicious type-1033 message embedded within an NTRIP or serial RTCM3 correction stream. For this to work, the message must be crafted to include a valid CRC, which tricks the system into accepting the packet as legitimate. Notably, simply connecting to the stream is insufficient; the attack requires a specifically formatted message structure that bypasses the software's length-checking logic to successfully cause the memory overflow.

Is my system at risk based on Halo Surface Signal?

According to Halo Surface Signal, the risk depends on your specific implementation. While RTKLIB can ingest network-based NTRIP streams, these feeds are typically specialized for industrial or surveying tasks rather than public web traffic. Your exposure is largely determined by whether your GNSS receiver or server is reachable via an untrusted network. If your RTKLIB instance is isolated or restricted to internal, private networks, the likelihood of remote exploitation is significantly lower.

What should I do if I run RTKLIB in my environment?

Your first step is to locate all instances where RTKLIB is processing incoming correction data, specifically checking for NTRIP or RTCM3 integrations. Once identified, evaluate whether these services are exposed to the internet or wide-area networks. Coordinate with the relevant engineering or infrastructure teams to document these deployments and prioritize them for security updates. The goal is to determine the business criticality of each node and plan a path to patch or secure the connections.

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.