CVE-2026-55209

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 64% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
36%
KEV
Not listed

Published

August 18, 2026

Last Modified

September 14, 2026

Advisory Details (6)

Auto-updated Sep 14, 2026
Patch available. Sources: github_commit, github_pr, github_release, github.
github Patch Available

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow'), Improper Validation of Array Index, NULL Pointer Dereference and Out-of-bounds Read in resdata · Advisory · equinor/resdata · GitHub

https://github.com/equinor/resdata/security/advisories/GHSA-pr85-w493-9w3x
github_release Patch Available

6.2.9

Patch available: equinor/resdata 6.2.9

https://github.com/equinor/resdata/releases/tag/6.2.9
github_pr Patch Available

Backport to 6.2

Patch available: equinor/resdata 6.2.9 (PR #1166 merged 2026-05-18)

https://github.com/equinor/resdata/pull/1166
github_commit Patch Available

commit ee8cc12b026d (equinor/resdata)

Patch available: equinor/resdata 6.2.9 (contains commit ee8cc12b026d)

https://github.com/equinor/resdata/commit/ee8cc12b026d945df3077bc98e211ee45f80a433
github_commit Patch Available

commit d3f45828e941 (equinor/resdata)

Patch available: equinor/resdata 6.2.9 (contains commit d3f45828e941)

https://github.com/equinor/resdata/commit/d3f45828e9413506b8e8160a9304f4b7b06dcefc
github_commit Patch Available

commit 9f8fd6db472e (equinor/resdata)

Patch available: equinor/resdata 6.2.9 (contains commit 9f8fd6db472e)

https://github.com/equinor/resdata/commit/9f8fd6db472e0696080b768389914d60a453904f

Vendor Advisories for CVE-2026-55209(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
resdata3.0.1 ... 6.2.8 (29 versions)6.2.9—

Weakness Classification(4)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 10× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-19 19:48 UTCEG score recompute
  2. 2026-09-18 22:53 UTCEG score recompute
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-17 21:45 UTCEG score recompute
  5. 2026-09-17 19:31 UTCEPSS rescore
  6. 2026-09-16 15:05 UTCEG score recompute
  7. 2026-09-16 14:08 UTCEPSS rescore
  8. 2026-09-16 10:07 UTCEG score recompute
  9. 2026-09-16 05:15 UTCEPSS rescore
  10. 2026-09-14 20:27 UTCEG score recompute
  11. 2026-08-18 20:42 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55209?
CVE-2026-55209 is a critical vulnerability published on August 18, 2026. 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/rdkwgrdecl.cpp and…
When was CVE-2026-55209 disclosed?
CVE-2026-55209 was first published in the National Vulnerability Database on August 18, 2026, with the most recent update on September 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55209 actively exploited?
CVE-2026-55209 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 64.0% of all scored CVEs.
What is the CVSS score of CVE-2026-55209?
CVE-2026-55209 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-55209?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55209, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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