CVE-2026-22102

Executive Summary

CVE-2026-22102 is a critical arbitrary file overwrite vulnerability (CVSS 9.3) affecting an unspecified DIVD-related webserver product. The vulnerability exists in a certificate update functionality where a POST request to a specific endpoint accepts a filename parameter from the Content-Disposition header without proper verification, allowing attackers to write to arbitrary file locations. Successful exploitation can lead to denial of service via system file overwriting, or remote code execution by overwriting shell scripts whose execution can be triggered through other means.

Technical Analysis

The vulnerability resides in a certificate update mechanism exposed via a webserver endpoint. The affected functionality accepts POST requests designed to upload or update certificate files. The flaw is rooted in the improper handling of the Content-Disposition header:

1. Attack Vector Mechanics: When a client sends a POST request to the certificate update endpoint, the server processes the multipart or form data and extracts the filename from the Content-Disposition header. This filename is used directly to construct a file path without any path traversal validation, allowing attackers to include path traversal sequences (e.g., ../../../) or absolute paths to redirect writes to arbitrary locations on the filesystem.

2. Underlying Vulnerability Class: This is a classic CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) flaw. The server fails to verify that the resolved path stays within the intended upload directory.

3. Attack Surface: The endpoint is reachable over a network, requiring no authentication (CVSS vector indicates PR:N — no privileges required). The attack complexity is low, meaning no special conditions are needed to trigger the flaw.

4. Impact Escalation Chain:

   • Direct impact: Arbitrary file write with the permissions of the webserver process.
   • Denial of Service: Overwriting critical system files (e.g., /etc/passwd, configuration files, libraries) causes service disruption.
   • Remote Code Execution: If the attacker overwrites a shell script that is executed via cron jobs, application features, or other scheduled tasks, code execution becomes possible.

5. Data Integrity Impact: The CVSS vector assigns HIGH integrity impact (I:H) and HIGH availability impact (A:H), while confidentiality remains unaffected (C:N). This confirms the attack is primarily focused on file manipulation rather than data exfiltration.

Exploitation Scenarios

Scenario 1: Denial of Service via System File Overwrite

Step 1 — Reconnaissance: The attacker identifies the target webserver hosting the certificate update endpoint. This may be discovered through Shodan queries targeting the webserver product or through application fingerprinting.

Step 2 — Weaponization: The attacker crafts a POST request to the certificate update endpoint. The request includes a Content-Disposition header with a filename parameter containing path traversal sequences pointing to a system-critical file.

Example request structure:

POST /update/certificate HTTP/1.1
Host: target
Content-Type: multipart/form-data

Content-Disposition: form-data; name="certfile"; filename="../../../etc/init.d/webserver"

Step 3 — Payload Execution: The server processes the request and writes the body content to the traversed path, overwriting the targeted system file. If the attacker targets a service configuration or startup script, the next service restart causes failure or degradation.

Step 4 — Post-Exploitation Impact: The webserver service fails to start or the system becomes unstable, resulting in denial of service for all legitimate users.

Scenario 2: Remote Code Execution via Shell Script Overwrite

Step 1 — Reconnaissance: The attacker identifies writable shell script locations on the target system. Common targets include cron job scripts (/etc/cron.d/, /var/spool/cron/), webserver CGI scripts, or application startup scripts.

Step 2 — Weaponization: The attacker sends a POST request to the certificate endpoint with a filename parameter containing the path to a shell script that is scheduled for execution.

Example request structure:

POST /update/certificate HTTP/1.1
Host: target
Content-Disposition: form-data; name="certfile"; filename="../../../../var/spool/cron/root"

The body contains a malicious cron job or shell commands.

Step 3 — Payload Execution: Once written, the malicious content triggers when the cron daemon reads the overwritten file, or when the shell script is invoked through normal application flow.

Step 4 — Post-Exploitation Impact: The attacker achieves remote code execution with the privileges of the user running the scheduled task or script, potentially escalating to full system compromise.

Scenario 3: Web Shell Deployment

Step 1: Attacker deploys a web shell by traversing to the webserver's document root (e.g., ../../../../var/www/html/shell.php).

Step 2: The webshell is served to the attacker, providing persistent remote access where they can execute arbitrary commands on the system.

Impact Assessment

Business Impact: This vulnerability carries a CVSS base score of 9.3 (Critical) with the attack vector being network-based, requiring no privileges, and having low attack complexity. The score places it in the 9.0-10.0 critical range per CVSS severity labels.

Affected Systems: Any deployment of the affected DIVD webserver product with the vulnerable certificate update functionality.

Blast Radius: The vulnerability allows:

• File integrity compromise across the entire filesystem (subject to webserver process permissions)
• Potential privilege escalation if the webserver runs as root
• Complete denial of service through critical file corruption
• Remote code execution with persistent backdoor potential

Business Consequences:

• Service outages from file overwrites
• Data integrity breaches and potential system compromise
• Supply chain risk if the affected product is used in infrastructure components

EPSS Assessment: With an EPSS score of 0.00314 (23.8% percentile of exploited CVEs), the likelihood of immediate exploitation in the wild is currently low, but the public availability of PoC information increases the risk of exploitation as threat actors weaponize the vulnerability.

Detection Guidance

Sigma Rule

title: Suspicious Certificate Update with Path Traversal Filename
id: a1b2c3d4-e5f6-7890-abcd-ef1234567890
status: experimental
description: Detects POST requests to certificate update endpoints with path traversal sequences in Content-Disposition filename parameters
logsource:
  category: webserver
  product: apache
  service: access_log
detection:
  selection:
    cs_method: POST
    cs_uri_extension: certificate|update|cert
  selection_filenames:
    cs_headers|contains|all:
      - 'filename="'
  filter_traversal:
    cs_headers|contains:
      - '../../'
      - '..\\'
      - '%2e%2e'
      - '/etc/'
      - '/var/'
      - '/usr/'
  condition: selection and selection_filenames and not filter_traversal
  timeframe: 5m
level: high
fields:
  - c-ip
  - cs-useragent
falsepositives:
  - Legitimate certificate uploads with unusual but valid filenames
tags:
  - attack.t1190
  - attack.t1505.003

YARA Rule

rule Detect_Certificate_Update_Path_Traversal
{
    meta:
        author = "Valtersit Threat Intel"
        description = "Detects path traversal attempts in HTTP requests targeting certificate update endpoints"
        cve = "CVE-2026-22102"
        date = "2026-01-01"
        severity = "critical"
    strings:
        $ip_request = /POST\s+\S*(certificate|update|upload)[^\r\n]*\s+HTTP\/1\.[01]/i
        $traversal_unix = /\.\.\/\.\.\/\.\.\//
        $traversal_windows = /\.\.\\\.\.\\\.\.\\/
        $traversal_encoded = /%2e%2e%2f%2e%2e%2f/
        $content_disposition = /Content-Disposition:\s*form-data[^\r\n]*filename="\.\.[\/\\]/
        $shell_extension = /filename="[^"]*\.(sh|cron|php|py|rb|pl|bin)
    condition:
        ($ip_request at 0) and any of ($traversal_unix, $traversal_windows, $traversal_encoded, $content_disposition) and any of ($shell_extension)
}

Suricata IDS Rule

alert http any any -> any any (
    msg:"CVE-2026-22102 Attempted Certificate Update Path Traversal";
    flow:to_server,established;
    http.method:"POST";
    http.uri; content:"certificate"; nocase;
    http.request_line; content:"Content-Disposition"; nocase;
    http.header; content:"filename"; nocase;
    http.header; content:"../"; nocase;
    pcre:"/filename\s*=\s*[\x22\x27][^]*\.\.\/[^]*[\x22\x27]/i";
    classtype:attempted-admin;
    reference:cve,2026-22102;
    sid:2025022;
    rev:1;
    metadata:attack_target_server, created_at_2026_01_01, deployment_perimeter, signature_severity_major;
)

Elastic Detection

sequence by source.ip with maxspan=1m
  [ network where destination.port == 80 or destination.port == 443 or destination.port == 8080 and network.protocol == "http" ]
  [ http where request.method == "POST" and url.path == "/update/certificate" and 
    stringContains(hash(request.headers), "Content-Disposition") and 
    (stringContains(hash(request.headers), "..\\") or stringContains(hash(request.headers), "../")) ]
  [ file where event.action == "write" and file.path == "/etc/*" or file.path == "/var/spool/*" or file.path == "/usr/*" ]

Splunk SPL Query

index=web sourcetype=access_combined 
| where method="POST" 
| search uri=*certificate* OR uri=*update* OR uri=*upload*
| regex _raw="Content-Disposition: form-data; name=\"[^\"]*\"\; filename=\"[^\"]*\.\.\/"
| eval threat_name="CVE-2026-22102_Certificate_Update_Path_Traversal"
| eval severity="critical"
| table _time, src_ip, dest_ip, uri, http_user_agent, status
| dedup src_ip, uri

Wazuh OSSEC Rule

<group name="cve-2026-22102,">
  <rule id="100221" level="12">
    <decoded_as>web_access</decoded_as>
    <match>POST</match>
    <match>certificate</match>
    <regex>filename="\.\./</regex>
    <description>CVE-2026-22102: Attempted path traversal in certificate update endpoint</description>
    <group>attack.t1190,</group>
    <mitre>
      <id>T1190</id>
    </mitre>
    <options>no_full_log</options>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Status: No patch is available. Patch confidence is 0/4 — no patch evidence from any tracked source was identified. The vendor (DIVD) has not released a fix as of this report.

Immediate Mitigations:

1. Endpoint Restriction: Implement a reverse proxy (Nginx, HAProxy, or similar) in front of the affected webserver that blocks or restricts access to the certificate update endpoint. Use allowlist-based access control to limit which IP addresses can reach this functionality.

2. Input Validation Without Patch: Deploy a WAF (Web Application Firewall) rule that inspects Content-Disposition headers for path traversal sequences (e.g., ../, ..\, encoded variants) and rejects such requests.

3. Filesystem Restrictions: Run the webserver process with a dedicated low-privilege user account. Mount critical system directories (e.g., /etc, /var/spool, /usr/bin) as read-only where feasible.

4. File Integrity Monitoring: Deploy file integrity monitoring (FIM) agents to detect unauthorized changes to system files and cron scripts.

Patch/Upgrade Steps: Since no patch exits, monitor vendor advisories from DIVD for updates. When a fix is released, apply it immediately in a staged rollout. Alternatively, consider replacing the affected product with an alternative certificate management solution.

Long-Term Hardening:

1. Architecture Review: Move certificate update functionality behind a separate, dedicated service running with minimal privileges and strictly validated file handling.

2. Chroot/Sandboxing: Run the certificate update service within a chroot jail or container with no access to the host filesystem.

3. Path Canonicalization: Any replacement implementation must canonicalize paths and verify that the resolved path stays within an allowed directory.

4. Network Segmentation: Isolate the affected service on a separate network segment with strict egress filtering.

5. Monitoring: Implement logging for all POST requests containing Content-Disposition headers with filename parameters, with alerts on suspicious patterns.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-22102 — Official CVE record and technical description
2. CWE-22 Reference: https://cwe.mitre.org/data/definitions/22.html — Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
3. MITRE ATT&CK: https://attack.mitre.org/techniques/T1190/ — Exploit Public-Facing Application
4. FIRST EPSS: https://www.first.org/epss/ — EPSS scoring resource for CVE-2026-22102

No evidence of active threat actor campaigns or exploitation in the wild was identified as of this report. The CVE is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog. However, PoC information is publicly available, which increases the risk of exploitation in the near term despite currently low EPSS percentiles.