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: 0.8% (54th percentile of EPSS-scored CVEs). 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: 0.8%CVSS: 9.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
9.8CRITICALmedium confidence
EG Risk
49
EG Risk 49/100CISA SSVC

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%
Exploitation1% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track* or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.8%
EPSS %ILE
54th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* or Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact total (CVSS ≥ 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 18, 2026

Last Modified

September 30, 2026

Advisory Details (6)

Auto-updated Sep 30, 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 rangeFix by version rangeDependents
resdata3.0.1 ... 6.2.8 (29 versions)
  • every version up to 6.2.9: fixed in 6.2.9
—

Weakness Classification(4)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 36× 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. 2026-10-05 01:53 UTCEG score recompute
  2. 2026-10-04 23:22 UTCEPSS rescore
  3. 2026-10-03 17:37 UTCEG score recompute
  4. 2026-10-03 14:26 UTCEPSS rescore
  5. 2026-10-02 19:18 UTCEG score recompute
  6. 2026-10-02 17:56 UTCEPSS rescore
  7. 2026-10-02 01:25 UTCEG score recompute
  8. 2026-10-01 19:50 UTCEPSS rescore
  9. 2026-09-30 18:11 UTCEG score recompute
  10. 2026-09-30 15:03 UTCEPSS rescore
  11. 2026-09-30 09:47 UTCEG score recompute
  12. 2026-09-29 15:22 UTCEPSS rescore
  13. 2026-09-28 21:55 UTCEG score recompute
  14. 2026-09-28 13:51 UTCEPSS rescore
  15. 2026-09-27 16:28 UTCEG score recompute
  16. 2026-09-27 13:48 UTCEPSS rescore
  17. 2026-09-27 07:54 UTCEG score recompute
  18. 2026-09-26 15:59 UTCEPSS rescore
  19. 2026-09-24 17:01 UTCEG score recompute
  20. 2026-09-24 14:04 UTCEPSS rescore
  21. 2026-09-23 20:19 UTCEG score recompute
  22. 2026-09-23 17:54 UTCEPSS rescore
  23. 2026-09-22 14:57 UTCEG score recompute
  24. 2026-09-21 22:24 UTCEG score recompute
  25. 2026-09-20 22:41 UTCEG score recompute
Show 12 more
  1. 2026-09-20 20:16 UTCEPSS rescore
  2. 2026-09-19 19:48 UTCEG score recompute
  3. 2026-09-18 22:53 UTCEG score recompute
  4. 2026-09-18 19:28 UTCEPSS rescore
  5. 2026-09-17 21:45 UTCEG score recompute
  6. 2026-09-17 19:31 UTCEPSS rescore
  7. 2026-09-16 15:05 UTCEG score recompute
  8. 2026-09-16 14:08 UTCEPSS rescore
  9. 2026-09-16 10:07 UTCEG score recompute
  10. 2026-09-16 05:15 UTCEPSS rescore
  11. 2026-09-14 20:27 UTCEG score recompute
  12. 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 on August 18, 2026, with the most recent update on September 30, 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 0.8% probability of exploitation in the next 30 days (54th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55209?
CVE-2026-55209 has a CVSS base score of 9.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55209?
A fix for CVE-2026-55209 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55209 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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