CVE-2026-55209 resdata insufficiently validates untrusted GRDECL files
Attackers can trigger memory corruption or crashes in resdata by providing malformed GRDECL files, potentially leading to code execution or service termination.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55209?
CVE-2026-55209 is a critical memory corruption vulnerability in equinor resdata, published on 14 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-55209?
3 open source packages ship an affected version, including resdata.
| Package | Affected | Fixed in |
|---|---|---|
resdata PyPI | All versions | 6.2.9 |
resdata PyPI | All versions | 6.2.9 |
resdata PyPI | All versions | 6.2.9 |
How do I fix CVE-2026-55209?
Upgrade resdata to 6.2.9 or later.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-55209 being exploited?
There is no known exploitation of CVE-2026-55209 in the wild and no public exploit code.
Sources
Also known as GHSA-pr85-w493-9w3x, PYSEC-2026-3694.