---
title: "CVE-2026-55209: resdata - Buffer Overflow"
description: "resdata < 6.2.9 contains a buffer overflow and out-of-bounds read caused by insufficient validation of numeric fields and array indexes in GRDECL file parsing, letting remote attackers cause memory corruption or denial of service, exploit requires untrusted GRDECL file input."
url: https://panop.io/threat-heartbeat/CVE-2026-55209/
---

# CVE-2026-55209 resdata - Buffer Overflow

resdata < 6.2.9 contains a buffer overflow and out-of-bounds read caused by insufficient validation of numeric fields and array indexes in GRDECL file parsing, letting remote attackers cause memory corruption or denial of service, exploit requires untrusted GRDECL file input.

CVSS base score 9.8 /10

Critical

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.78% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-55209)

## Details

Type

Buffer Overflow

Impact

Denial Of Service, Out Of Bounds Rw

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Published

14 September 2026

Updated

15 October 2026

Weakness

[CWE-120](https://cwe.mitre.org/data/definitions/120.html)

## Vendor fix

Update to version 6.2.9 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-55209](https://nvd.nist.gov/vuln/detail/CVE-2026-55209)
- [https://github.com/equinor/resdata/security/advisories/GHSA-pr85-w493-9w3x](https://github.com/equinor/resdata/security/advisories/GHSA-pr85-w493-9w3x)
- [https://github.com/equinor/resdata/commit/9f8fd6db472e0696080b768389914d60a453904f](https://github.com/equinor/resdata/commit/9f8fd6db472e0696080b768389914d60a453904f)
- [https://github.com/equinor/resdata/commit/d3f45828e9413506b8e8160a9304f4b7b06dcefc](https://github.com/equinor/resdata/commit/d3f45828e9413506b8e8160a9304f4b7b06dcefc)
- [https://github.com/equinor/resdata/commit/ee8cc12b026d945df3077bc98e211ee45f80a433](https://github.com/equinor/resdata/commit/ee8cc12b026d945df3077bc98e211ee45f80a433)
- [https://github.com/equinor/resdata/pull/1166](https://github.com/equinor/resdata/pull/1166)
- [https://github.com/equinor/resdata/releases/tag/6.2.9](https://github.com/equinor/resdata/releases/tag/6.2.9)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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