CVE-2023-1718: Bitrix24 advisory

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.

What it is

Improper file stream access in /desktop_app/file.ajax.php?action=uploadfile in Bitrix24 22.0.300 allows unauthenticated remote attackers to cause denial-of-service via a crafted “tmp_url”.

Description quoted from the CVE record (assigned by STAR_Labs, published 2023-11-01).

Weakness: CWE-835 Loop with Unreachable Exit Condition (‘Infinite Loop’)

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality none, integrity none, availability high. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CISA assessment (SSVC): CISA assesses that a public proof of concept exists. Automatable: yes. Technical impact: partial.

Public exploit evidence (Exploit Observer)

Exploit Observer found 5 code repositories naming this CVE.

Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.

See all 9 references on Exploit Observer

Live scores

EPSS: 0.287
likely to be attacked soon
VEDAS: 0.982
strong exploit evidence
On CISA KEV: Not listed
Detection rule: Nuclei · Suricata

Who is affected

Product	Affected	Not affected
Bitrix24	up to and including 22.0.300	Not 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)

Bitrix24 - Denial of Service
Improper file stream access in /desktop_app/file.ajax.php?action=uploadfile in Bitrix24 22.0.300 allows unauthenticated remote attackers to cause denial-of-service via a crafted “tmp_url”.

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

The template sends 2 requests (GET /bitrix/tools/composite_data.php, POST /desktop_app/file.ajax.php?action=uploadfile); it decides using regex, word matchers. Severity in the template: high. 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-2023-1718.yaml

Show the template (85 lines)

yaml

id: CVE-2023-1718

info:
  name: "Bitrix24 - Denial of Service"
  author: vedas-arpsyndicate
  severity: high
  description: |
    Improper file stream access in /desktop_app/file.ajax.php?action=uploadfile in Bitrix24 22.0.300 allows
    unauthenticated remote attackers to cause denial-of-service via a crafted "tmp_url".
  reference:
    - https://www.exploit.observer/?keyword=CVE-2023-1718&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=bitrix&match=exact
  classification:
    cve-id: CVE-2023-1718
  metadata:
    verified: false
  tags: cve,cve2023,bitrix
http:
  - raw:
      - |
        GET /bitrix/tools/composite_data.php HTTP/1.0
        Host: {{Hostname}}
        Connection: close
        User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:64.0) Gecko/20100101 Firefox/64.0
      
      - |
        POST /desktop_app/file.ajax.php?action=uploadfile HTTP/1.0
        Host: {{Hostname}}
        User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:64.0) Gecko/20100101 Firefox/64.0
        Accept-Encoding: gzip, deflate, br, zstd
        Accept: */*
        Connection: keep-alive
        Cookie: PHPSESSID={{phpsessid}};
        X-Bitrix-Csrf-Token: {{bitrix_sessid}}
        X-Bitrix-Site-Id: s1
        Content-Length: 850
        Content-Type: multipart/form-data; boundary=aaf14817e09570802d671bdb022d22ac
        --aaf14817e09570802d671bdb022d22ac
        Content-Disposition: form-data; name="bxu_info[mode]"
        upload
        --aaf14817e09570802d671bdb022d22ac
        Content-Disposition: form-data; name="bxu_info[CID]"
        41382
        --aaf14817e09570802d671bdb022d22ac
        Content-Disposition: form-data; name="bxu_info[filesCount]"
        1
        --aaf14817e09570802d671bdb022d22ac
        Content-Disposition: form-data; name="bxu_info[packageIndex]"
        pIndex41382
        --aaf14817e09570802d671bdb022d22ac
        Content-Disposition: form-data; name="bxu_info[NAME]"
        file41382
        --aaf14817e09570802d671bdb022d22ac
        Content-Disposition: form-data; name="bxu_files[0][name]"
        file41382
        --aaf14817e09570802d671bdb022d22ac
        Content-Disposition: form-data; name="bxu_files[0][default][tmp_name]"
        file41382
        --aaf14817e09570802d671bdb022d22ac
        Content-Disposition: form-data; name="bxu_files[0][default][tmp_url]"
        just a test
        --aaf14817e09570802d671bdb022d22ac--
    
    matchers:
      - type: word
        part: body
        words:
          - '"uploadStatus":"uploaded"'
          - "'uploadStatus':'uploaded'"
        condition: or
    extractors:
      - type: regex
        name: bitrix_sessid
        group: 1
        part: body
        internal: true  
        regex:
          - "'bitrix_sessid':'([A-Za-z0-9]+)'"
      - type: regex
        name: phpsessid
        group: 1
        part: header
        internal: true
        regex:
          - 'PHPSESSID=([A-Za-z0-9]+)'

CVE-2023-1718.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2023-1718 Bitrix24 - Denial of Service. Add them to your Suricata rule set and reload.

Show the rules

suricata

alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2023-1718 Bitrix24 - Denial of Service"; flow:established,to_server; http.uri; content:"/bitrix/tools/composite_data.php"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2023-1718; reference:url,https://www.exploit.observer/?keyword=CVE-2023-1718&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=bitrix&match=exact; sid:1011748; rev:1;)

CVE-2023-1718.rules on GitHub

References

Technical analysis and advisories

https://starlabs.sg/advisories/23/23-1718/ (third-party-advisory)

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.