CVE-2026-12866

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-06-23. the CNA's CVSS baseline 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:snyk, epss, ghsa
Trending — 3 sources updated this weekElevated
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: Elevated riskExposed: 0

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

All versions of the package expr-eval are vulnerable to Code Execution via the toJSFunction() API. An attacker can execute arbitrary JavaScript by supplying crafted expressions that are compiled into native code using new Function(). Because user-controlled expressions are transformed directly into executable JavaScript, attackers can escape the intended expression sandbox and run arbitrary code within the application's context.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
75(Attend)
EG Risk 75/100SSVC: Attend

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%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
56%
KEV
Not listed

Published

June 23, 2026

Last Modified

August 14, 2026

Advisory Details (3)

Auto-updated Aug 28, 2026
⚠️ Active exploitation confirmed. No patch confirmed yet.
generic🟡 PoC Available

Unsafe code execution in Node.js when using `toJSFunction()` with untrusted variables · Issue #292 · silentmatt/expr-eval · GitHub

https://github.com/silentmatt/expr-eval/issues/292
generic🔴 Active Exploitation

Code Execution in org.webjars.npm:expr-eval | CVE-2026-12866 | Snyk

https://security.snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-17662018
generic🔴 Active Exploitation

Code Execution in expr-eval | CVE-2026-12866 | Snyk

https://security.snyk.io/vuln/SNYK-JS-EXPREVAL-15054690

Vendor Advisories for CVE-2026-12866(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 158× 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.

Showing the most recent 100 of 369 total refreshes for this CVE.

  1. 2026-09-01 04:39 UTCEPSS rescore
  2. 2026-08-31 00:52 UTCGHSA enrichment
  3. 2026-08-30 20:28 UTCEG score recompute
  4. 2026-08-30 20:28 UTCGHSA enrichment
  5. 2026-08-30 19:17 UTCEPSS rescore
  6. 2026-08-30 01:21 UTCEPSS rescore
  7. 2026-08-28 21:40 UTCEPSS rescore
  8. 2026-08-27 14:24 UTCEPSS rescore
  9. 2026-08-25 13:48 UTCEPSS rescore
  10. 2026-08-25 07:03 UTCGHSA enrichment
  11. 2026-08-25 02:37 UTCGHSA enrichment
  12. 2026-08-24 22:13 UTCEG score recompute
  13. 2026-08-24 22:13 UTCGHSA enrichment
  14. 2026-08-24 13:55 UTCEG score recompute
  15. 2026-08-24 13:55 UTCGHSA enrichment
  16. 2026-08-24 06:49 UTCGHSA enrichment
  17. 2026-08-24 01:37 UTCGHSA enrichment
  18. 2026-08-23 21:07 UTCGHSA enrichment
  19. 2026-08-23 16:43 UTCGHSA enrichment
  20. 2026-08-23 12:19 UTCGHSA enrichment
  21. 2026-08-23 07:53 UTCGHSA enrichment
  22. 2026-08-23 03:22 UTCEG score recompute
  23. 2026-08-23 03:22 UTCGHSA enrichment
  24. 2026-08-23 00:19 UTCEPSS rescore
  25. 2026-08-22 22:45 UTCGHSA enrichment
Show 75 more
  1. 2026-08-22 14:51 UTCEG score recompute
  2. 2026-08-22 14:51 UTCGHSA enrichment
  3. 2026-08-21 23:48 UTCEPSS rescore
  4. 2026-08-21 22:20 UTCGHSA enrichment
  5. 2026-08-21 17:34 UTCGHSA enrichment
  6. 2026-08-21 11:51 UTCGHSA enrichment
  7. 2026-08-21 06:32 UTCGHSA enrichment
  8. 2026-08-21 02:08 UTCEG score recompute
  9. 2026-08-21 02:08 UTCGHSA enrichment
  10. 2026-08-20 22:55 UTCEPSS rescore
  11. 2026-08-20 21:22 UTCGHSA enrichment
  12. 2026-08-20 16:57 UTCGHSA enrichment
  13. 2026-08-20 12:23 UTCGHSA enrichment
  14. 2026-08-20 07:49 UTCEG score recompute
  15. 2026-08-20 07:49 UTCGHSA enrichment
  16. 2026-08-19 17:03 UTCEPSS rescore
  17. 2026-08-19 15:37 UTCGHSA enrichment
  18. 2026-08-19 10:57 UTCGHSA enrichment
  19. 2026-08-19 04:50 UTCEG score recompute
  20. 2026-08-19 04:50 UTCGHSA enrichment
  21. 2026-08-18 13:48 UTCEPSS rescore
  22. 2026-08-17 15:01 UTCEG score recompute
  23. 2026-08-17 15:01 UTCGHSA enrichment
  24. 2026-08-17 10:36 UTCGHSA enrichment
  25. 2026-08-17 06:12 UTCGHSA enrichment
  26. 2026-08-17 01:01 UTCGHSA enrichment
  27. 2026-08-16 20:37 UTCGHSA enrichment
  28. 2026-08-16 16:12 UTCEG score recompute
  29. 2026-08-16 16:12 UTCGHSA enrichment
  30. 2026-08-16 14:56 UTCEPSS rescore
  31. 2026-08-16 11:48 UTCGHSA enrichment
  32. 2026-08-16 07:24 UTCGHSA enrichment
  33. 2026-08-16 03:00 UTCEG score recompute
  34. 2026-08-16 03:00 UTCGHSA enrichment
  35. 2026-08-16 02:14 UTCEPSS rescore
  36. 2026-08-15 22:36 UTCGHSA enrichment
  37. 2026-08-15 18:12 UTCGHSA enrichment
  38. 2026-08-15 13:48 UTCGHSA enrichment
  39. 2026-08-15 09:18 UTCGHSA enrichment
  40. 2026-08-15 04:52 UTCEG score recompute
  41. 2026-08-15 04:52 UTCGHSA enrichment
  42. 2026-08-15 01:30 UTCEPSS rescore
  43. 2026-08-15 00:27 UTCGHSA enrichment
  44. 2026-08-14 20:03 UTCGHSA enrichment
  45. 2026-08-14 15:39 UTCGHSA enrichment
  46. 2026-08-14 12:23 UTCGHSA enrichment
  47. 2026-08-14 07:59 UTCGHSA enrichment
  48. 2026-08-14 03:34 UTCGHSA enrichment
  49. 2026-08-13 23:10 UTCEG score recompute
  50. 2026-08-13 23:10 UTCGHSA enrichment
  51. 2026-08-13 22:00 UTCEPSS rescore
  52. 2026-08-13 18:40 UTCGHSA enrichment
  53. 2026-08-13 13:46 UTCGHSA enrichment
  54. 2026-08-13 09:13 UTCGHSA enrichment
  55. 2026-08-13 04:49 UTCGHSA enrichment
  56. 2026-08-13 00:25 UTCGHSA enrichment
  57. 2026-08-12 20:01 UTCGHSA enrichment
  58. 2026-08-12 15:37 UTCGHSA enrichment
  59. 2026-08-12 14:50 UTCEG score recompute
  60. 2026-08-12 14:50 UTCGHSA enrichment
  61. 2026-08-12 13:50 UTCEPSS rescore
  62. 2026-08-12 10:24 UTCGHSA enrichment
  63. 2026-08-12 05:59 UTCGHSA enrichment
  64. 2026-08-12 01:29 UTCGHSA enrichment
  65. 2026-08-11 21:05 UTCGHSA enrichment
  66. 2026-08-11 16:40 UTCEG score recompute
  67. 2026-08-11 16:40 UTCGHSA enrichment
  68. 2026-08-11 13:42 UTCEPSS rescore
  69. 2026-08-11 12:16 UTCGHSA enrichment
  70. 2026-08-11 07:52 UTCGHSA enrichment
  71. 2026-08-11 03:28 UTCEG score recompute
  72. 2026-08-11 03:28 UTCGHSA enrichment
  73. 2026-08-10 23:59 UTCEPSS rescore
  74. 2026-08-10 23:04 UTCGHSA enrichment
  75. 2026-08-10 18:39 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2026-12866?
CVE-2026-12866 is a critical vulnerability published on June 23, 2026. All versions of the package expr-eval are vulnerable to Code Execution via the toJSFunction() API. An attacker can execute arbitrary JavaScript by supplying crafted expressions that are compiled into native code using new Function(). Because user-controlled expressions are transformed directly into…
When was CVE-2026-12866 disclosed?
CVE-2026-12866 was first published in the National Vulnerability Database on June 23, 2026, with the most recent update on August 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-12866 actively exploited?
CVE-2026-12866 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 43.8% of all scored CVEs.
What is the CVSS score of CVE-2026-12866?
CVE-2026-12866 has a CVSS v4.0 base score of 9.8 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-12866?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-12866, 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.

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