MEDIUM CVSS 5.8
Published: 2026-07-08

CVE-2026-55438

coder coder Security Advisory (CVE-2026-55438)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-55438 impacting coder coder. Evaluated with CVSS Base Score of 5.8 (MEDIUM).

Original NVD Description

Source: NIST NVD
Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2, Coder's subdomain-based workspace app proxy allowed the same-owner CORS check to be bypassed. When a workspace-name subdomain segment parsed as a UUID, the workspace was resolved by ID without confirming the URL's username matched the real owner, while the CORS middleware trusted the unverified username in the hostname. Practical exploitation requires subdomain app routing (wildcard hostname) enabled and a victim who visits the attacker's crafted app URL while authenticated. The fix in versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2 validates the subdomain username against the resolved workspace's actual owner and bases the same-owner CORS decision on the authoritative owner identity. No known workarounds are available.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
High (AC:H)
Depends on race conditions or environment
Privileges Required
Low (PR:L)
Standard user access required
User Interaction
Required (UI:R)
User must click or open resource
Scope
Changed (S:C)
Impacts components beyond caller authority
Confidentiality
High (C:H)
Total information disclosure
Integrity
None (I:N)
No system modification impact
Availability
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product coder / coder
Affected Versions *
Weakness Enumeration CWE-346

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2026-55438 impacting coder coder.

⚡ Nuclei Detection Template (YAML) cve-2026-55438.yaml
id: cve-2026-55438

info:
  name: coder coder - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-55438 affecting coder coder.
    Evaluation: Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2, Coder&#x...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-55438
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N
    cvss-score: 5.8
    cve-id: CVE-2026-55438
    cwe-id: CWE-346
  tags: cve,cve-2026-55438,coder,coder,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "coder"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-55438.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-55438
# Target: coder coder | CVSS: 5.8 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-55438 (coder coder)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against coder coder scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2026-55438.sh
# Recommended Remediation & Patching Commands for CVE-2026-55438
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install coder 2>/dev/null || \
sudo dnf upgrade coder 2>/dev/null || \
sudo yum update coder

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i coder 2>/dev/null || rpm -qa | grep -i coder

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-55438 in coder coder?

Review vendor-specific security notices and update coder coder packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2026-55438?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2026-55438?

CVE-2026-55438 is classified with a CVSS 3.1 Base Score of 5.8 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
5.8
MEDIUM SEVERITY
CVE ID CVE-2026-55438
Weakness CWE-346
Vendor coder
Product coder
Published 2026-07-08
Vector CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N