CVE-2026-55781

LOWPre-NVD 2.42.4—
EchelonGraph scoreMEDIUM confidence

This low-severity CVE scores 2.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2% (4th 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
Elevated
2.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 2.4Exploit: Elevated riskExposed services: Not assessed

The CVE record names the fixed release — apply it.

NanaZip is the 7-Zip derivative intended for the modern Windows experience. Prior to 6.5.1749.0, NanaZip's UFS and FFS image handler in NanaZip.Codecs.Archive.Ufs.cpp validates the superblock block size only against the MINBSIZE lower bound and does not validate the fs_fsize fragment size, allowing attacker-controlled 32-bit fields to flow into indirect-block, directory, and extraction buffer allocations. A tiny crafted UFS image can force multi-gigabyte allocations during open or extraction, causing memory exhaustion or process termination. This issue is fixed in version 6.5.1749.0.

CVSS v3
2.4
EG Score
2.4LOWmedium confidence
EG Risk
27
EG Risk 27/100CISA 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
Severity24% × 45%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: The CVE record names the fixed release. Apply it within your standard update timelines.
EPSS PROB
0.2%
EPSS %ILE
4th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

The CVE record names the fixed release. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). 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

July 10, 2026

Last Modified

July 10, 2026

References (3)

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 28× 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. 2026-10-09 20:07 UTCEPSS rescore
  2. 2026-10-08 17:12 UTCEPSS rescore
  3. 2026-10-07 23:48 UTCEPSS rescore
  4. 2026-10-06 15:18 UTCEPSS rescore
  5. 2026-10-05 17:43 UTCEPSS rescore
  6. 2026-10-04 23:22 UTCEPSS rescore
  7. 2026-10-03 14:26 UTCEPSS rescore
  8. 2026-10-02 17:56 UTCEPSS rescore
  9. 2026-10-01 19:50 UTCEPSS rescore
  10. 2026-10-01 15:11 UTCEG score recompute
  11. 2026-09-30 15:03 UTCEPSS rescore
  12. 2026-09-29 15:22 UTCEPSS rescore
  13. 2026-09-28 13:51 UTCEPSS rescore
  14. 2026-09-28 09:48 UTCEG score recompute
  15. 2026-09-26 15:59 UTCEPSS rescore
  16. 2026-09-24 14:04 UTCEPSS rescore
  17. 2026-09-23 17:54 UTCEPSS rescore
  18. 2026-09-23 05:45 UTCEG score recompute
  19. 2026-09-20 20:16 UTCEPSS rescore
  20. 2026-09-18 19:28 UTCEPSS rescore
  21. 2026-09-18 05:18 UTCEG score recompute
  22. 2026-09-17 19:31 UTCEPSS rescore
  23. 2026-09-16 14:08 UTCEPSS rescore
  24. 2026-09-16 05:15 UTCEPSS rescore
  25. 2026-09-15 03:11 UTCEPSS rescore
Show 71 more
  1. 2026-09-13 16:47 UTCEPSS rescore
  2. 2026-09-12 02:56 UTCEG score recompute
  3. 2026-09-10 09:35 UTCEPSS rescore
  4. 2026-09-08 22:01 UTCEPSS rescore
  5. 2026-09-07 16:01 UTCEPSS rescore
  6. 2026-09-06 13:47 UTCEPSS rescore
  7. 2026-09-05 21:42 UTCEG score recompute
  8. 2026-09-04 05:07 UTCEPSS rescore
  9. 2026-09-02 14:12 UTCEPSS rescore
  10. 2026-09-01 13:54 UTCEPSS rescore
  11. 2026-09-01 04:40 UTCEPSS rescore
  12. 2026-08-30 19:17 UTCEPSS rescore
  13. 2026-08-30 07:58 UTCEG score recompute
  14. 2026-08-30 01:22 UTCEPSS rescore
  15. 2026-08-28 21:41 UTCEPSS rescore
  16. 2026-08-27 14:25 UTCEPSS rescore
  17. 2026-08-27 04:01 UTCEG score recompute
  18. 2026-08-26 14:46 UTCEPSS rescore
  19. 2026-08-25 13:49 UTCEPSS rescore
  20. 2026-08-23 23:23 UTCEG score recompute
  21. 2026-08-23 00:19 UTCEPSS rescore
  22. 2026-08-21 23:49 UTCEPSS rescore
  23. 2026-08-20 22:55 UTCEPSS rescore
  24. 2026-08-20 19:28 UTCEG score recompute
  25. 2026-08-19 17:04 UTCEPSS rescore
  26. 2026-08-18 13:48 UTCEPSS rescore
  27. 2026-08-17 15:33 UTCEG score recompute
  28. 2026-08-17 13:47 UTCEPSS rescore
  29. 2026-08-16 14:56 UTCEPSS rescore
  30. 2026-08-16 02:14 UTCEPSS rescore
  31. 2026-08-15 01:30 UTCEPSS rescore
  32. 2026-08-14 11:38 UTCEG score recompute
  33. 2026-08-13 22:00 UTCEPSS rescore
  34. 2026-08-12 13:51 UTCEPSS rescore
  35. 2026-08-11 07:44 UTCEG score recompute
  36. 2026-08-11 00:00 UTCEPSS rescore
  37. 2026-08-09 13:46 UTCEPSS rescore
  38. 2026-08-08 16:37 UTCEPSS rescore
  39. 2026-08-08 03:50 UTCEG score recompute
  40. 2026-08-06 13:47 UTCEPSS rescore
  41. 2026-08-05 19:17 UTCEPSS rescore
  42. 2026-08-04 23:55 UTCEG score recompute
  43. 2026-08-03 10:36 UTCEPSS rescore
  44. 2026-08-02 02:27 UTCEPSS rescore
  45. 2026-08-01 20:00 UTCEG score recompute
  46. 2026-08-01 04:16 UTCEPSS rescore
  47. 2026-07-30 16:28 UTCEPSS rescore
  48. 2026-07-30 01:30 UTCEPSS rescore
  49. 2026-07-29 16:05 UTCEG score recompute
  50. 2026-07-28 15:37 UTCEPSS rescore
  51. 2026-07-26 14:54 UTCEPSS rescore
  52. 2026-07-26 12:10 UTCEG score recompute
  53. 2026-07-25 14:18 UTCEPSS rescore
  54. 2026-07-24 14:18 UTCEPSS rescore
  55. 2026-07-23 03:20 UTCEG score recompute
  56. 2026-07-22 14:08 UTCEPSS rescore
  57. 2026-07-21 15:25 UTCEPSS rescore
  58. 2026-07-20 17:08 UTCEPSS rescore
  59. 2026-07-19 14:31 UTCEPSS rescore
  60. 2026-07-19 14:31 UTCEPSS rescore
  61. 2026-07-19 02:29 UTCEPSS rescore
  62. 2026-07-18 10:04 UTCEPSS rescore
  63. 2026-07-16 17:03 UTCEPSS rescore
  64. 2026-07-15 16:57 UTCEPSS rescore
  65. 2026-07-15 16:57 UTCEPSS rescore
  66. 2026-07-13 22:31 UTCEPSS rescore
  67. 2026-07-13 06:13 UTCEPSS rescore
  68. 2026-07-13 06:13 UTCEPSS rescore
  69. 2026-07-12 05:46 UTCEPSS rescore
  70. 2026-07-10 17:13 UTCEG score recompute
  71. 2026-07-10 17:12 UTCMITRE cvelistV5first tracked

Publicly available exploits

(2 references)

Working exploit code is in the public domain (2 GitHub PoCs). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCg17hubH4ck/CVE-2026-55781-poc
    First seen Sep 17, 2026

    Unbounded memory allocation in NanaZip's UFS handler via an attacker-controlled `fs_bsize` field.

    Open source ↗
  • GitHub PoCyzy0okrkv1hngo0r/CVE-2026-55781-poc
    First seen Sep 17, 2026

    Unbounded memory allocation in NanaZip's UFS handler via an attacker-controlled `fs_bsize` field.

    Open source ↗

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55781?
CVE-2026-55781 is a low vulnerability published on July 10, 2026. NanaZip is the 7-Zip derivative intended for the modern Windows experience. Prior to 6.5.1749.0, NanaZip's UFS and FFS image handler in NanaZip.Codecs.Archive.Ufs.cpp validates the superblock block size only against the MINBSIZE lower bound and does not validate the fs_fsize fragment size, allowing…
When was CVE-2026-55781 disclosed?
CVE-2026-55781 was first published on July 10, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55781 actively exploited?
CVE-2026-55781 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (4th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55781?
CVE-2026-55781 has a CVSS base score of 2.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55781?
The CVE record for CVE-2026-55781 names the fix: "This issue is fixed in version 6.5.1749.0."

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