CVE-2026-55209: Buffer Overflow (CVSS 9.8)

Description

resdata is software for reading and writing result files from the Eclipse reservoir simulator. Prior to 6.2.9, resdata insufficiently validates numeric fields, grid dimensions, keyword sizes, and array indexes while parsing untrusted GRDECL files in lib/resdata/rd_kw_grdecl.cpp and lib/resdata/rd_grid.cpp. Malformed COORD, ZCORN, CORSNUM, ACTNUM, or MAPAXES data can reach rd_grid_alloc_GRDECL_kw__ with inconsistent lengths, while unbounded floating-point conversion can exceed the intended parser buffer. In a network service that accepts untrusted GRDECL files, these conditions can cause a classic buffer overflow, out-of-bounds reads, invalid array access, NULL pointer dereference, memory corruption, or service termination. This issue is fixed in version 6.2.9.

Is your site exposed to CVE-2026-55209?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

9.8

CRITICAL

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

EPSS — Exploit Prediction

0.0042

Probability of exploitation

0.36%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-120 CWE-120

CWE-125 Out-of-bounds Read

CWE-129 CWE-129

CWE-476 CWE-476

References

Other References

https://github.com/equinor/resdata/commit/9f8fd6db472e0696080b768389914d60a453904f https://github.com/equinor/resdata/commit/d3f45828e9413506b8e8160a9304f4b7b06dcefc https://github.com/equinor/resdata/commit/ee8cc12b026d945df3077bc98e211ee45f80a433 https://github.com/equinor/resdata/pull/1166 https://github.com/equinor/resdata/releases/tag/6.2.9 https://github.com/equinor/resdata/security/advisories/GHSA-pr85-w493-9w3x

Frequently Asked Questions

What is CVE-2026-55209? +

resdata is software for reading and writing result files from the Eclipse reservoir simulator. Prior to 6.2.9, resdata insufficiently validates numeric fields, grid dimensions, keyword sizes, and array indexes while parsing untrusted GRDECL files in lib/resdata/rd_kw_grdecl.cpp and lib/resdata/rd_grid.cpp. Malformed COORD, ZCORN, CORSNUM, ACTNUM, or MAPAXES data can reach rd_grid_alloc_GRDECL_kw__ with inconsistent lengths, while unbounded floating-point conversion can exceed the intended parser buffer. In a network service that accepts untrusted GRDECL files, these conditions can cause a classic buffer overflow, out-of-bounds reads, invalid array access, NULL pointer dereference, memory corruption, or service termination. This issue is fixed in version 6.2.9. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-55209? +

CVE-2026-55209 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0042, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-55209? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-27820

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain …

CVE-2025-11698

A denial-of-service issue exists in 5380/5480/5580 controllers boot firmware lower than version 1.072. This vulnerability could potentially allow a malicious …

CVE-2025-12012

A denial-of-service issue exists in 5380/5480/5580 controllers. This vulnerability could potentially allow a malicious user to write invalid file data …

CVE-2025-12011

A denial-of-service issue exists in 5370/5570 controllers. This vulnerability could potentially allow a remote user to load an invalid project, …

CVE-2024-13503

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') vulnerability in Newtec NTC2218, NTC2250, NTC2299 on Linux, PowerPC, ARM …

CVE-2024-6199

An unauthenticated attacker on the WAN interface, with the ability to intercept Dynamic DNS (DDNS) traffic between DDNS services and …

CVE-2026-55209