HIGH CVSS 8.5
Published: 2026-04-06

CVE-2026-34975

useplunk plunk Security Advisory (CVE-2026-34975)
↗ Official NIST NVD Record
Seeking technical exploit breakdowns or verified PoC code for CVE-2026-34975?
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-34975 impacting useplunk plunk. Evaluated with CVSS Base Score of 8.5 (HIGH).

Original NVD Description

Source: NIST NVD
Plunk is an open-source email platform built on top of AWS SES. Prior to 0.8.0, a CRLF header injection vulnerability was discovered in SESService.ts, where user-supplied values for from.name, subject, custom header keys/values, and attachment filenames were interpolated directly into raw MIME messages without sanitization. An authenticated API user could inject arbitrary email headers (e.g. Bcc, Reply-To) by embedding carriage return/line feed characters in these fields, enabling silent email forwarding, reply redirection, or sender spoofing. The fix adds input validation at the schema level to reject any of these fields containing \r or \n characters, consistent with the existing validation already applied to the contentId field. This vulnerability is fixed in 0.8.0.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
Low (PR:L)
Standard user access required
User Interaction
None (UI:N)
Zero human interaction required
Scope
Changed (S:C)
Impacts components beyond caller authority
Confidentiality
High (C:H)
Total information disclosure
Integrity
Low (I:L)
Partial data modification possible
Availability
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product useplunk / plunk
Affected Versions *
Weakness Enumeration CWE-93

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-2026-34975 impacting useplunk plunk.

⚡ Nuclei Detection Template (YAML) cve-2026-34975.yaml
id: cve-2026-34975

info:
  name: useplunk plunk - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-34975 affecting useplunk plunk.
    Evaluation: Plunk is an open-source email platform built on top of AWS SES. Prior to 0.8.0, a CRLF header injection vulnerability was discovered in SESService.ts,...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-34975
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
    cvss-score: 8.5
    cve-id: CVE-2026-34975
    cwe-id: CWE-93
  tags: cve,cve-2026-34975,useplunk,plunk,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "plunk"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-34975.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-34975
# Target: useplunk plunk | CVSS: 8.5 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-34975 (useplunk plunk)...")
    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 useplunk plunk 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-2026-34975.sh
# Recommended Remediation & Patching Commands for CVE-2026-34975
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install plunk 2>/dev/null || \
sudo dnf upgrade plunk 2>/dev/null || \
sudo yum update plunk

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

# 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.

🔗 Verified Technical References

Authorities
  • No records filed in this category.
Distributions
  • No records filed in this category.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-34975 in useplunk plunk?

Review vendor-specific security notices and update useplunk plunk 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-2026-34975?

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-2026-34975?

CVE-2026-34975 is classified with a CVSS 3.1 Base Score of 8.5 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
8.5
HIGH SEVERITY
CVE ID CVE-2026-34975
Weakness CWE-93
Vendor useplunk
Product plunk
Published 2026-04-06
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N