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CVE-2026-55209

resdata insufficiently validates untrusted GRDECL files

9.8 CriticalFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.78%Up 0.4 points since Sep 15, 2026
90%50%10%1%

What each source reports

CVE List Score used 9.8

resdata insufficiently validates untrusted GRDECL files

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.

Record
CVE-2026-55209
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-120, CWE-125, CWE-129, CWE-476
Updated
2026-11-02
EUVDEUVD-2026-77802 9.8

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.

Record
EUVD-2026-77802
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-pr85-w493-9w3x 9.8

resdata has Classic Buffer Overflow, Improper Validation of Array Index, NULL Pointer Dereference and Out-of-bounds Read

Impact

Prior to version 6.2.9 resdata would not correctly validate input in GRDECL files. The severity rating assumes that resdata is used to parse untrused files in a networking context such as a webservice.

Patches

The bug has been patched starting with version 6.2.9.

Record
GHSA-pr85-w493-9w3x
CVSS 3.0
9.8 CriticalCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-120, CWE-125, CWE-129, CWE-476
Updated
2026-11-02
NVD 9.8

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.

Record
CVE-2026-55209
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-120, CWE-125, CWE-129, CWE-476
Updated
2026-11-02
OSV 9.8

resdata insufficiently validates untrusted GRDECL files

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.

Record
CVE-2026-55209
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-120, CWE-125, CWE-129, CWE-476
Updated
2026-11-02
OSVGHSA-pr85-w493-9w3x 9.8

resdata has Classic Buffer Overflow, Improper Validation of Array Index, NULL Pointer Dereference and Out-of-bounds Read

Impact

Prior to version 6.2.9 resdata would not correctly validate input in GRDECL files. The severity rating assumes that resdata is used to parse untrused files in a networking context such as a webservice.

Patches

The bug has been patched starting with version 6.2.9.

Record
GHSA-pr85-w493-9w3x
CVSS 3.0
9.8 CriticalCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-120, CWE-125, CWE-129, CWE-476
Updated
2026-11-02
OSVPYSEC-2026-3694 9.8

resdata has Classic Buffer Overflow, Improper Validation of Array Index, NULL Pointer Dereference and Out-of-bounds Read

Impact

Prior to version 6.2.9 resdata would not correctly validate input in GRDECL files. The severity rating assumes that resdata is used to parse untrused files in a networking context such as a webservice.

Patches

The bug has been patched starting with version 6.2.9.

Record
PYSEC-2026-3694
CVSS 3.0
9.8 CriticalCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
resdata
PyPI
before 6.2.9
6.2.9
resdata
PyPI
before 6.2.9, plus listed versions
3.0.14.0.04.1.04.1.14.1.2
Show 24 moreShow less
4.2.04.2.14.2.24.2.34.2.45.0.05.0.0b05.0.15.0.25.0.35.1.05.1.15.1.25.1.36.0.16.1.06.2.06.2.26.2.36.2.46.2.56.2.66.2.76.2.8
6.2.9

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-55209 is a critical vulnerability (CVSS 9.8) in Equinor Resdata, published August 18, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.78%, the 56th percentile. Fixed in resdata 6.2.9.

References

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