CVE-2026-56789: RTKLIB Heap Buffer Overflow in RINEX Parsing

Technical summary

The vulnerability resides in the readrnxobsb function within src/rinex.c, where satellite count values extracted from RINEX epoch headers are not properly clamped before being used to allocate or write to heap buffers. RINEX (Receiver Independent Exchange Format) is a standard text format for GNSS observation data; each epoch record includes a satellite count. A crafted file declaring more than 64 satellites per epoch will cause out-of-bounds heap writes and potentially out-of-bounds stack reads, leading to memory corruption, information disclosure, or process termination. The root cause is insufficient input validation on the satellite count field.

Business impact

Organizations relying on RTKLIB-based applications for positioning tasks face service disruption. Survey crews, drone operators, autonomous vehicle developers, and precision agriculture platforms that use rnx2rtkp or RTKPOST are vulnerable to denial-of-service attacks via malicious RINEX files. If an attacker can inject or distribute poisoned RINEX data (e.g., from a compromised server or man-in-the-middle position), they can crash processing pipelines. While the CVSS vector indicates no confidentiality or integrity impact, the practical risk of information leakage from stack reads and subsequent application crashes warrants prompt remediation.

Affected systems

RTKLIB through version 2.4.3 is affected. All applications built on or embedding RTKLIB that parse RINEX observation files are in scope, notably the rnx2rtkp and RTKPOST command-line and GUI tools. This includes custom integrations in surveying software, GIS platforms, and research systems that depend on RTKLIB for GNSS data processing. Systems running older versions are at highest risk; check your local RTKLIB version and any downstream applications you maintain.

Exploitability

Exploitation requires delivery of a crafted RINEX file to a vulnerable application. The CVSS vector indicates network accessibility (AV:N) and low attack complexity (AC:L), but user interaction (UI:R) is needed—a user or automated process must open or process the malicious file. This is a realistic attack vector for organizations that ingest RINEX files from public repositories, untrusted sources, or over unencrypted channels. The barrier to crafting a malicious RINEX is low; an attacker need only modify the satellite count field in an otherwise valid file. However, no public exploit code is known, and the flaw does not appear on the CISA Known Exploited Vulnerabilities (KEV) catalog, suggesting active exploitation remains limited.

Remediation

Update RTKLIB to a patched version released after the vulnerability disclosure. Check the RTKLIB project repository or your vendor's advisory for the exact patched version number and installation instructions. For applications embedding RTKLIB, coordinate with upstream maintainers and update your dependency. As an interim mitigation, restrict RINEX file ingestion to trusted sources, validate file format strictly, and run RTKLIB applications in isolated or sandboxed environments to contain denial-of-service impact.

Patch guidance

Visit the official RTKLIB repository to obtain the latest patched release. Verify against the vendor advisory that the version number addresses CVE-2026-56789. If you maintain a custom build or fork, apply the upstream patch to src/rinex.c that adds proper clamping of the satellite count value before heap operations. Document the patched version in your change control system. Regression test with known-good RINEX files to confirm functionality is preserved.

Detection guidance

Monitor for crashes or segmentation faults in RTKLIB applications (rnx2rtkp, RTKPOST) correlating with RINEX file ingestion. Examine input RINEX files for anomalously high satellite count declarations in epoch headers (>64). Deploy file-integrity monitoring on RINEX data sources. Consider adding input validation upstream of RTKLIB—pre-screen RINEX files for satellite count violations before passing them to the library. Security information and event management (SIEM) systems should flag repeated application crashes from the same process.

Why prioritize this

This vulnerability merits timely but not emergency remediation. The CVSS score of 6.5 (Medium) reflects that active exploitation is unlikely without direct user interaction, and no public KEV status indicates widespread in-the-wild abuse. However, organizations in surveying, geospatial analytics, and autonomous systems that depend on RTKLIB should prioritize patching within 30–60 days to avoid downstream supply-chain risks. If your RTKLIB deployment processes RINEX files from the internet or untrusted networks, elevate priority.

Risk score, explained

The CVSS 3.1 score of 6.5 (Medium) reflects a network-accessible flaw with no authentication or special privileges required, but user interaction is mandatory (opening or processing a file). The attack does not breach confidentiality or integrity in a traditional sense, but causes availability loss via denial of service. The 'out-of-bounds stack reads' mentioned in the description hint at potential information disclosure, though the official CVSS vector shows C:N. In practice, heap corruption vulnerabilities can sometimes leak sensitive memory; defenders should treat this as a credible risk and not rely solely on the CVSS number.

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