CVE-2026-1555

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-04-22. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Elevated
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.

The WebStack theme for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the io_img_upload() function in all versions up to, and including, 1.2024. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
59(Track)
EG Risk 59/100SSVC: Track

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%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
60%
KEV
Not listed

Published

April 15, 2026

Last Modified

April 22, 2026

Advisory Details (2)

Auto-updated Sep 9, 2026
No patch confirmed yet.
generic

GitHub - owen0o0/WebStack: WordPress 版 WebStack 导航主题 https://nav.iowen.cn · GitHub

https://github.com/owen0o0/WebStack/tree/master
generic

WebStack/inc/ajax.php at master · owen0o0/WebStack · GitHub

https://github.com/owen0o0/WebStack/blob/master/inc/ajax.php#L5

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 6× in last 7d / 27× 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 243 total refreshes for this CVE.

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

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCNxploited/CVE-2026-1555
    First seen Apr 17, 2026

    WebStack <= 1.2024 - Unauthenticated Arbitrary File Upload

    Open source ↗

Frequently asked(5)

What is CVE-2026-1555?
CVE-2026-1555 is a critical vulnerability published on April 15, 2026. The WebStack theme for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the ioimgupload() function in all versions up to, and including, 1.2024. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which…
When was CVE-2026-1555 disclosed?
CVE-2026-1555 was first published in the National Vulnerability Database on April 15, 2026, with the most recent update on April 22, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-1555 actively exploited?
CVE-2026-1555 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 39.6% of all scored CVEs.
What is the CVSS score of CVE-2026-1555?
CVE-2026-1555 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-1555?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-1555, 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.

Dependency Blast Radius

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