CVE-2023-48217

Executive Summary

CVE-2023-48217 is a remote code execution (RCE) vulnerability in Statamic CMS, affecting the "Forms" feature front-end upload fields and the asset upload fields in the control panel. The flaw resides in insufficient mime type validation, allowing crafted PHP files disguised as images to bypass validation checks and be uploaded. Successful exploitation enables malicious users to execute arbitrary code on the underlying server, potentially leading to full system compromise. The vulnerability is patched in Statamic versions 3.4.14 and 4.34.0; there are no known workarounds.

Technical Analysis

Statamic is a flat-first, Laravel + Git powered CMS built on PHP, designed primarily for content-driven websites. The platform provides two distinct upload surfaces that are affected by this vulnerability: the front-end "Forms" feature, which allows site visitors to submit form data including file attachments, and the asset upload fields within the administrative control panel.

The underlying weakness is a mime type validation bypass. When a file is uploaded through either of these surfaces, Statamic applies validation rules that are intended to restrict acceptable file types—typically by checking the declared MIME type of the uploaded file. However, the validation logic is insufficient to prevent the acceptance of PHP files that are crafted to resemble images. Attackers can craft a malicious PHP payload and manipulate the file's metadata or headers so that the MIME type detection returns an image type (e.g., image/jpeg, image/png), thereby passing the validation check despite the file's actual content being executable PHP code.

The specific traversal of the validation logic is not disclosed in the available technical detail, and no patch diff or commit analysis is available in the provided intelligence data. It is plausible that the validation relies on the content-type header supplied by the client or on a naive extension check, rather than inspecting actual file content through robust magic-byte detection. In either case, the validation rule is bypassable, allowing the uploaded file to be stored within the web root where it can subsequently be invoked via a direct HTTP request to execute the embedded PHP code.

The attack surface is dual: unauthenticated or low-privilege attackers can target the front-end Forms feature (provided the site has public-facing forms with file upload capabilities), while the control panel asset upload fields require authenticated access, elevating the severity when combined with a low-privilege account compromise. The CVSS score of 8.8 (High) reflects the significant impact: network-accessible, low complexity, low privilege requirement, no user interaction, and high confidentiality, integrity, and availability impact.

Exploitation Scenarios

No public PoC is available in the provided data; the attack chain is inferred from the vulnerability class and NVD description.

Step 1 — Reconnaissance / Target Identification: An attacker identifies a target running Statamic CMS. This can be achieved through internet-wide scanning for known Statamic fingerprints, such as the generator meta tag or characteristic response headers/paths. Shodan dorks such as http.title:"Statamic" can assist in this enumeration.

Step 2 — Flaw Trigger: The attacker locates a front-end form that includes a file upload field (via the Forms feature). Alternatively, if the attacker has low-privilege control panel access, they can target the asset upload fields. The attacker prepares a PHP file (e.g., a web shell or a one-liner such as <?php system($_GET['cmd']); ?>) and crafts it to mimic an image. This typically involves setting the appropriate file extension (e.g., .jpg or .png), injecting image magic bytes at the beginning of the file, and/or spoofing the Content-Type header during the upload request.

Step 3 — Payload Execution: The crafted file passes the mime type validation because it is made to look like an image. The file is stored in a directory accessible via the web server. The attacker then requests the uploaded file directly via its URL (e.g., https://target/uploads/web-shell.jpg or a similar path), causing the PHP engine on the server to parse and execute the embedded code. This results in remote code execution under the context of the web server process.

Step 4 — Post-Exploitation: With arbitrary code execution, the attacker can perform various post-exploitation activities: reading sensitive configuration files (e.g., .env containing database credentials and application keys), accessing the data stored in the Git repository backing the CMS, potentially pivoting to the database server, and leveraging the compromised web server to move laterally within the internal network. The attacker can also install persistent backdoors, create rogue administrator accounts in the control panel, or abuse the server for further malicious activities such as crypto mining or as a botnet node.

The attack is particularly impactful because it can be executed remotely without any user interaction and requires only low privileges for the control panel variant, or no authentication at all for the front-end Forms variant.

Impact Assessment

Business Impact: Successful exploitation results in full remote code execution on the web server, enabling data theft, website defacement, malware deployment, and potential lateral movement. This represents a complete compromise of confidentiality, integrity, and availability, hence the high CVSS impact subscores of 8.8/10.

Affected Systems: All Statamic CMS instances running versions prior to 3.4.14 (3.x branch) or prior to 4.34.0 (4.x branch) are vulnerable, provided they expose a Forms feature with file upload capability or an accessible control panel. The vast majority of production Statamic sites are likely exposed through public-facing forms.

Blast Radius: The vulnerability has a low privilege requirement (PR:L), meaning an attacker needs only a low-privilege control panel account for the asset upload vector — or no account at all for the Forms vector. The resulting RCE grants privileges equivalent to the web server user, which on typical shared or single-tenant Linux deployments is sufficient to read all application source code, configuration, and data. The lack of user interaction (UI:N) and the network attack vector (AV:N) further increase the attractiveness of this vulnerability to attackers targeting the broader ecosystem of Statamic-hosted websites.

Exploitation Prevalence: EPSS score of 0.01104 (62.7th percentile) suggests moderate likelihood of exploitation in the wild. The CISA KEV (Known Exploited Vulnerabilities) catalog does not currently list this CVE, and there is no evidence of active threat actor campaigns in the provided data.

Detection Guidance

Sigma Rule

title: Suspicious PHP File Upload via Statamic Forms
id: 3c6c1e2a-7c9b-4a7b-9a2e-1b7d4c2b6f1a
status: experimental
description: Detects attempts to upload PHP files through Statamic CMS upload endpoints, potentially exploiting CVE-2023-48217.
logsource:
  category: webserver
  product: apache
  detection:
    selection:
      cs-method: POST
      cs-uri-query|contains:
        - '/forms/'
        - '/assets/'
        - '/files/'
      sc-status: 200
      cs-uri-query|re:
        - '.*\.php.*'
    condition: selection
  level: high
  tags:
    - attack.t1203
    - cve.2023-48217
    - attack.initial-access

YARA Rule

rule statamic_cve_2023_48217_php_upload
{
    meta:
        author = "valtersit.com"
        description = "Detects PHP files crafted to look like images, potential exploitation of CVE-2023-48217"
        date = "2025-03-15"
    strings:
        $php_open = /<\?php/
        $php_short = /<\?=/
        $shell_cmd = /(system|exec|shell_exec|passthru|eval|assert|popen|proc_open)\s*\(/ nocase
        $jpeg_magic = { FF D8 FF }
        $png_magic = { 89 50 4E 47 }
        $gif_magic = { 47 49 46 38 }
    condition:
        ($php_open or $php_short) and
        ($shell_cmd) and
        ($jpeg_magic or $png_magic or $gif_magic) and
        filesize < 2MB
}

Suricata IDS Rule

alert tcp any any -> any any (msg:"Potential CVE-2023-48217 Statamic PHP Upload Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/forms/"; http_uri; pcre:"/\.php(?:\?.*)?$/Ui"; http_client_body; content:"<?php"; nocase; classtype:attempted-admin; sid:10048217; rev:1; metadata:created_at 2025_03_15, updated_at 2025_03_15, cve CVE-2023-48217;)

Elastic Detection

sequence by source.ip with maxspan=5m
  [network where event.type == "start" and protocol == "http" and destination.port == 80]
  [http where request.method == "POST" and uri.path in ("/forms/*", "/assets/*", "/files/*") and
   request.body.content_type == "image/*" and
   request.body.content contains "<?php"]

Splunk SPL Query

index=web sourcetype=access_combined
| where method="POST" AND (uri_path LIKE "%/forms/%" OR uri_path LIKE "%/assets/%" OR uri_path LIKE "%/files/%")
| rename request.MIME_TYPE as mime_type
| where mime_type LIKE "image/%" AND request_body LIKE "%<?php%"
| table _time, src_ip, uri_path, mime_type, status
| sort -_time

Wazuh OSSEC Rule

<group name="statamic,cve-2023-48217,">
  <rule id="523255" level="12">
    <if_sid>31100</if_sid>
    <field name="url">\.php$</field>
    <field name="content_type">^image/</field>
    <description>Statamic CMS: Suspicious PHP file upload identified as image</description>
    <group>attack.initial_access,</group>
    <mitre>
      <id>T1203</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 0/4 — UNPATCHED. No patch evidence is available from any tracked source. Note that this confidence designation reflects the intelligence data provided; the NVD description officially confirms that Statamic has released patched versions (3.4.14 and 4.34.0), but the tracked patch sources have not yet verified or recorded this patch.

1) Immediate Mitigations:

• Disable file upload functionality on any front-end Forms if not strictly required; if necessary, replace with external upload services or restrict uploads to authenticated users only.
• Tighten control panel access: enforce MFA, limit access by IP allow-lists, and revoke low-privilege accounts that are not actively used.
• Deploy a Web Application Firewall (WAF) with rules to block POST requests containing PHP code in file uploads, particularly those with image MIME types.
• Review server configuration to ensure uploaded files are stored outside the web root; if not possible, configure the web server (Apache/Nginx) to not execute PHP scripts within the upload directory (e.g., php_flag engine off in .htaccess).

2) Patch / Upgrade Steps:

• Upgrade Statamic to version 3.4.14 (for 3.x users) or 4.34.0 (for 4.x users) as soon as possible. Verify the compatibility of custom plugins or themes with the upgraded version before deployment.
• After upgrading, audit existing uploaded files for suspicious PHP content disguised as images; remove or sanitize any malicious files found.
• Confirm the upgrade succeeded by verifying the version number in the admin panel or via php artisan statamic:version.

3) Long-Term Hardening:

• Implement a layered file validation approach: validate file content by magic bytes, not just MIME headers; enforce strict allow-lists for allowed file extensions and content types.
• Run the web server and PHP under a restricted service account with least privilege; enable PHP open_basedir restrictions.
• Regularly audit web server logs for anomalous upload activity, particularly requests containing both image MIME types and PHP content.
• Maintain a current inventory of CMS instances and versions to ensure timely patching in the future.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2023-48217
2. Statamic GitHub Advisory / Vendor Announcement: Referenced in the CNA title "Remote code execution via form uploads in statamic/cms" — contains patch version details (3.4.14, 4.34.0). Note: Direct advisory URL not available in provided intelligence data.
3. Statamic Changelog / Release Notes: Available at https://statamic.com/changelog — verify patched versions and release dates.
4. EPSS Data: https://www.first.org/epss/api — for probability of exploitation metrics (0.01104 at 62.7th percentile).
5. CISA KEV Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — confirms CVE-2023-48217 is not listed (not KEV).

Threat Actor Activity: No known threat actor campaigns or exploit-in-the-wild evidence is documented in the provided intelligence data. The absence of CISA KEV listing and unknown PoC status suggests exploitation may be limited, but the moderate EPSS percentile warrants vigilance.