CVE-2026-6686

MEDIUMPre-NVD 4.64.6—
EchelonGraph scoreMEDIUM confidence

Score 4.6 from GitHub Security Advisory published 2026-07-01. A secondary CVSS source baseline 4.6; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
4.6EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 4.6Exploit: None knownExposed services: Not assessed

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

FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters. This maps to CWE-908 (Use of Uninitialized Resource). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (4.6, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.

CVSS v3
4.6
EG Score
4.6MEDIUMmedium confidence
EG Risk
21
EG Risk 21/100

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 (value × EchelonGraph’s weight)
Severity46% × 45%
The EG Score, 4.6 of 10.
Exploitation0.3% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.
EPSS PROB
0.3%
EPSS %ILE
15th
KEV
Not listed

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

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.

Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” 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

July 1, 2026

Last Modified

July 2, 2026

Advisory Details (3)

Auto-updated Jul 3, 2026
No fix on record yet.
Web page

GitHub - runZeroInc/vulns-2026-fatfs-chance · GitHub

https://github.com/runZeroInc/vulns-2026-fatfs-chance
Web page

Seven FatFs bugs, one very large blast radius

https://www.runzero.com/blog/fatfs-bugs/
Web page

FatFS uninitialized cluster exposure after seek beyond EOF

https://www.runzero.com/advisories/fatfs-uninit-cluster-exposure-cve-2026-6686/

Vendor Advisories for CVE-2026-6686(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 11× in last 7d / 34× 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 98 of 197 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. 2 repeat rows among the latest 100 are merged into the row they repeat. The 99 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-11 19:31 UTCEG score recompute
  2. 2026-10-11 16:46 UTCEG score recompute
  3. 2026-10-11 14:07 UTCEG score recompute
  4. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  5. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  6. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  7. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  8. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  9. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  10. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  11. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  12. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  13. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  14. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  15. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  16. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  17. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  18. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  19. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  20. 2026-09-23 06:53 UTCEG score recompute
  21. 2026-09-23 06:53 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  22. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  23. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  24. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  25. 2026-09-18 06:35 UTCEG score recompute
Show 73 more
  1. 2026-09-18 06:35 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  2. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  3. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  4. 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  5. 2026-09-13 12:45 UTCEG score recompute
  6. 2026-09-13 12:45 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  7. 2026-09-12 15:02 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  8. 2026-09-12 14:47 UTCEG score recompute
  9. 2026-09-12 14:47 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  10. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  11. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  12. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  13. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  14. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  15. 2026-09-06 02:31 UTCEG score recompute
  16. 2026-09-06 02:31 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  17. 2026-09-05 15:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  18. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  19. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  20. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  21. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  22. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  23. 2026-08-30 13:12 UTCEG score recompute
  24. 2026-08-30 13:12 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  25. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  26. 2026-08-28 21:42 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  27. 2026-08-27 22:28 UTCEG score recompute
  28. 2026-08-27 22:28 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  29. 2026-08-26 14:47 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  30. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  31. 2026-08-25 02:04 UTCEG score recompute
  32. 2026-08-25 02:04 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  33. 2026-08-24 04:11 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  34. 2026-08-23 05:25 UTCEG score recompute
  35. 2026-08-23 05:25 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  36. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  37. 2026-08-22 07:21 UTCEG score recompute
  38. 2026-08-22 07:21 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  39. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  40. 2026-08-21 04:33 UTCEG score recompute
  41. 2026-08-21 04:33 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  42. 2026-08-20 22:56 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  43. 2026-08-20 04:45 UTCEG score recompute
  44. 2026-08-20 04:45 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  45. 2026-08-19 17:04 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  46. 2026-08-18 21:00 UTCEG score recompute
  47. 2026-08-18 21:00 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  48. 2026-08-18 13:49 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  49. 2026-08-17 14:19 UTCEG score recompute
  50. 2026-08-17 14:19 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  51. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  52. 2026-08-16 16:25 UTCEG score recompute
  53. 2026-08-16 16:25 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  54. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  55. 2026-08-16 02:15 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  56. 2026-08-15 18:33 UTCEG score recompute
  57. 2026-08-15 18:33 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  58. 2026-08-15 01:31 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  59. 2026-08-14 20:40 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  60. 2026-08-13 22:48 UTCEG score recompute
  61. 2026-08-13 22:47 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  62. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  63. 2026-08-13 00:54 UTCEG score recompute
  64. 2026-08-13 00:54 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  65. 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  66. 2026-08-12 03:02 UTCEG score recompute
  67. 2026-08-12 03:02 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  68. 2026-08-11 05:09 UTCEG score recompute
  69. 2026-08-11 05:09 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  70. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  71. 2026-08-10 07:17 UTCEG score recompute
  72. 2026-08-10 07:17 UTCGHSA enrichmentGHSA-h94p-vjqx-v7rr · GitHub CVSS 4.6
  73. 2026-08-09 13:47 UTCEPSS rescoreEPSS 0.4% · 30th percentile

Frequently asked(5)

What is CVE-2026-6686?
CVE-2026-6686 is a medium-severity vulnerability; its CVE record was published on July 1, 2026. FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters. This maps to CWE-908 (Use of Uninitialized Resource). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (4.6, Medium). The…
When was CVE-2026-6686 made public?
CVE-2026-6686 was made public on July 1, 2026: that is the date its CVE record's CNA, runZero, Inc., gives for when the vulnerability was made public. The CVE record itself was published on July 1, 2026. EchelonGraph's copy of the record carries a last-modified date of July 2, 2026; the record at its source may have been updated since.
Is CVE-2026-6686 actively exploited?
CVE-2026-6686 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (15th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-6686?
CVE-2026-6686 has a CVSS base score of 4.6 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-6686?
No fix for CVE-2026-6686 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-6686 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-6686

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