CVE-2026-72844

MEDIUMPre-NVD 6.36.3
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

Score 6.3 from GitHub Security Advisory published 2026-08-20. A secondary CVSS source baseline 6.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 3 sources updated this weekElevated

Also known asEUVD-2026-63487 (ENISA EUVD) · GHSA-4fhc-8rq3-cjvg (GitHub Security Advisories)Source: ENISA EUVD

6.3EG
EchelonGraph verdictPlan mitigationThe upstream fix is not in a release yet: until the release ships, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule, then apply it (the SSVC decision on this page).
  • Public exploit or proof-of-concept code is available
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 6.3Exploit: Public PoCExposed services: Not assessed

An upstream fix is merged but not yet released — mitigate (WAF / firewall / segmentation) until the release ships, then apply it.

The Lean 4 kernel does not verify that the structure named in a projection expression matches the type of the value being projected, and environment::add_inductive in src/kernel/inductive.cpp did not type check the nested inductive applications that are replaced by auxiliary types, so their parametric arguments escaped checking. A metaprogram running in the Lean process can register an ill-typed nested inductive whose constructor applies a .proj C 0 projection to a value of the unrelated type W, and the kernel admits the declaration through the ordinary checked addDecl path at maximum kernel checking, without sorry, unsafeCast, debug.skipKernelTC, addDeclWithoutChecking, FFI, or a modified .olean file. The result is a type confusion yielding a proof of False that carries no axioms, from which any proposition can be derived. The published proof of concept additionally pads two expressions until their hashes and approximate depths collide, which defeats kernel caching; that is the technique used to reach the flaw, not its cause. Exploitation requires running a metaprogram in-process, for example by building a project or importing a malicious Lake dependency.

CVSS v3
6.3
EG Score
6.3MEDIUMmedium confidence
EG Risk
44
EG Risk 44/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity63% × 45%
Impact severity (EG Severity): CVSS 6.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: An upstream fix is merged but not yet in a tagged release. Until the release ships, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule, then apply it.
EPSS PROB
0.2%
EPSS %ILE
8th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (6.3): severity, escalated by confirmed exploitation. This CVE's 6.3 is its impact severity (EG Severity), not escalated.

EG Severity
6.3 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-29). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

An upstream fix is merged but not yet in a tagged release. Until the release ships, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule, then apply it.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 20, 2026

Last Modified

October 26, 2026

Advisory Details (8)

Auto-updated Aug 20, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit, github_pr.
Web page

Lean 4 Kernel Type Checking Bypass via Mismatched Structure Projections | Advisories | VulnCheck

https://www.vulncheck.com/advisories/lean-4-kernel-type-checking-bypass-via-mismatched-structure-projections
Web page

GitHub - leanprover/lean4: Lean 4 programming language and theorem prover · GitHub

https://github.com/leanprover/lean4
Web page

oss-security - Lean 4 kernel soundness bug: forging proofs via nested inductive projections (0 = 1 demonstrated)

https://www.openwall.com/lists/oss-security/2026/08/02/1
Web page

GitHub - xrchz/CollatzLean: Collatz conjecture in Lean · GitHub

https://github.com/xrchz/CollatzLean
Web page

GitHub - endrazine/lean-cve-poc: Example of proving "0 = 1" using a vulnerability in the Lean 4 kernel. · GitHub

https://github.com/endrazine/lean-cve-poc
GitHub pull request

fix: missing check at kernel inductive declaration

Fix merged in leanprover/lean4 PR #14577 on 2026-07-28 — awaiting tagged release

https://github.com/leanprover/lean4/pull/14577
GitHub commit

commit a39eab69e1ee (leanprover/lean4)

Fix landed in leanprover/lean4 commit a39eab69e1ee — awaiting tagged release

https://github.com/leanprover/lean4/commit/a39eab69e1eee9ad38f4efe507907b1026a77808
Web page

Kernel accepts wrong-structure projections, allowing an axiom-free proof of False · Issue #14576 · leanprover/lean4 · GitHub

https://github.com/leanprover/lean4/issues/14576

Vendor Advisories for CVE-2026-72844(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 / 53× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 99 of 173 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 100 is merged into the row it repeats. The 74 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-02 16:46 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  2. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  3. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  4. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  5. 2026-10-29 16:59 UTCEG score recompute
  6. 2026-10-29 16:59 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  7. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  8. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  9. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  10. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  11. 2026-10-26 02:26 UTCEG score recompute
  12. 2026-10-26 02:26 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  13. 2026-10-26 01:46 UTCEG score recompute
  14. 2026-10-26 01:46 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  15. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  16. 2026-10-25 14:06 UTCEG score recompute
  17. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  18. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  19. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  20. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  21. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  22. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  23. 2026-10-18 20:36 UTCEG score recompute
  24. 2026-10-18 20:36 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  25. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.2% · 6th percentile
Show 74 more
  1. 2026-10-18 03:15 UTCEG score recompute
  2. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  3. 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  4. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  5. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  6. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  7. 2026-10-12 15:41 UTCEG score recompute
  8. 2026-10-11 19:27 UTCEG score recompute
  9. 2026-10-11 16:42 UTCEG score recompute
  10. 2026-10-11 14:02 UTCEG score recompute
  11. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  12. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  13. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  14. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  15. 2026-10-08 05:24 UTCEG score recompute
  16. 2026-10-08 05:23 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  17. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  18. 2026-10-07 02:13 UTCEG score recompute
  19. 2026-10-07 02:13 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  20. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  21. 2026-10-06 03:27 UTCEG score recompute
  22. 2026-10-06 03:27 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  23. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  24. 2026-10-05 01:50 UTCEG score recompute
  25. 2026-10-05 01:50 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  26. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  27. 2026-10-04 03:30 UTCEG score recompute
  28. 2026-10-04 03:30 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  29. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  30. 2026-10-03 05:09 UTCEG score recompute
  31. 2026-10-03 05:09 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  32. 2026-10-02 06:49 UTCEG score recompute
  33. 2026-10-02 06:49 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  34. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  35. 2026-10-01 06:34 UTCEG score recompute
  36. 2026-10-01 06:34 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  37. 2026-09-30 08:14 UTCEG score recompute
  38. 2026-09-30 08:14 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  39. 2026-09-28 23:42 UTCEG score recompute
  40. 2026-09-28 23:42 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  41. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  42. 2026-09-28 01:22 UTCEG score recompute
  43. 2026-09-28 01:22 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  44. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  45. 2026-09-27 03:02 UTCEG score recompute
  46. 2026-09-27 03:02 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  47. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  48. 2026-09-24 21:21 UTCEG score recompute
  49. 2026-09-24 21:21 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  50. 2026-09-24 02:52 UTCEG score recompute
  51. 2026-09-24 02:52 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  52. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  53. 2026-09-23 04:31 UTCEG score recompute
  54. 2026-09-23 04:31 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  55. 2026-09-22 06:11 UTCEG score recompute
  56. 2026-09-22 06:11 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  57. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  58. 2026-09-21 07:50 UTCEG score recompute
  59. 2026-09-21 07:50 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  60. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  61. 2026-09-20 09:01 UTCEG score recompute
  62. 2026-09-20 09:01 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  63. 2026-09-19 10:12 UTCEG score recompute
  64. 2026-09-19 10:12 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  65. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  66. 2026-09-18 11:32 UTCEG score recompute
  67. 2026-09-18 11:31 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  68. 2026-09-17 13:10 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  69. 2026-09-16 14:29 UTCEG score recompute
  70. 2026-09-16 14:29 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3
  71. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  72. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  73. 2026-09-15 15:13 UTCEG score recompute
  74. 2026-09-15 15:13 UTCGHSA enrichmentGHSA-4fhc-8rq3-cjvg · GitHub CVSS 6.3

Publicly available exploits

(1 reference)

Public exploit code is referenced for this CVE (1 GitHub PoC). The fix is not yet in a release, so defenders should restrict or isolate affected systems accordingly until it ships.

  • GitHub PoCendrazine/lean-cve-poc
    Published Aug 2, 2026

    CVE-2026-72844 : Example of proving "0 = 1" using a vulnerability in the Lean 4 kernel.

    Open source ↗

Frequently asked(5)

What is CVE-2026-72844?
CVE-2026-72844 is a medium-severity vulnerability; its CVE record was published on August 20, 2026. The Lean 4 kernel does not verify that the structure named in a projection expression matches the type of the value being projected, and environment::add_inductive in src/kernel/inductive.cpp did not type check the nested inductive applications that are replaced by auxiliary types, so their…
When was CVE-2026-72844 made public?
CVE-2026-72844 was made public on July 28, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on August 20, 2026. EchelonGraph's copy of the record carries a last-modified date of October 26, 2026; the record at its source may have been updated since.
Is CVE-2026-72844 actively exploited?
CVE-2026-72844 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (8th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-72844?
CVE-2026-72844 has a CVSS base score of 6.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-72844?
An upstream fix for CVE-2026-72844 has been merged but is not yet in a tagged release. Until it ships, restrict network exposure of the affected system or apply the vendor's mitigation, then update to the release that contains the fix. The vendor advisories EchelonGraph has for CVE-2026-72844 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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