LOW CVSS 2.5
Published: 2026-05-14

CVE-2026-44638

saitoha libsixel Security Advisory (CVE-2026-44638)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-44638 impacting saitoha libsixel. Evaluated with CVSS Base Score of 2.5 (LOW).

Original NVD Description

Source: NIST NVD
libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a wrong NULL check after an allocation call in sixel_decode_raw and sixel_decode causes a NULL pointer dereference whenever the allocation fails. The check tests the address of the output parameter (always non-NULL) instead of the value the malloc returned. On allocation failure, the function continues and writes through a NULL pointer, crashing the process. This is a denial of service against any caller of these public APIs that hits a low-memory condition. This vulnerability is fixed in 1.8.7-r2.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Local (AV:L)
Requires local system execution permissions
Attack Complexity
High (AC:H)
Depends on race conditions or environment
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
Required (UI:R)
User must click or open resource
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
None (I:N)
No system modification impact
Availability
Low (A:L)
Partial service performance degradation

🎯 Affected Versions Matrix

Affected Product saitoha / libsixel
Affected Versions *
Weakness Enumeration CWE-476

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-2026-44638 impacting saitoha libsixel.

⚡ Nuclei Detection Template (YAML) cve-2026-44638.yaml
id: cve-2026-44638

info:
  name: saitoha libsixel - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: low
  description: |
    Automated signature & scanner for CVE-2026-44638 affecting saitoha libsixel.
    Evaluation: libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From  to 1.8.7-r1, a wrong NULL check after an allocation call in ...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-44638
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
    cvss-score: 2.5
    cve-id: CVE-2026-44638
    cwe-id: CWE-476
  tags: cve,cve-2026-44638,saitoha,libsixel,low

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "libsixel"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-44638.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-44638
# Target: saitoha libsixel | CVSS: 2.5 (LOW)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-44638 (saitoha libsixel)...")
    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 saitoha libsixel 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-2026-44638.sh
# Recommended Remediation & Patching Commands for CVE-2026-44638
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install libsixel 2>/dev/null || \
sudo dnf upgrade libsixel 2>/dev/null || \
sudo yum update libsixel

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

# 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-2026-44638 in saitoha libsixel?

Review vendor-specific security notices and update saitoha libsixel 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-2026-44638?

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-2026-44638?

CVE-2026-44638 is classified with a CVSS 3.1 Base Score of 2.5 (LOW). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
2.5
LOW SEVERITY
CVE ID CVE-2026-44638
Weakness CWE-476
Vendor saitoha
Product libsixel
Published 2026-05-14
Vector CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L