Login Sign Up

CVE-2021-43413

8.8 HIGH

📋 TL;DR

This vulnerability in GNU Hurd allows any user who can read a file to modify it by exploiting a shared pager port in memory-mapped file operations. This can be trivially escalated to gain full root access. Only systems running GNU Hurd are affected.

💻 Affected Systems

Products:
  • GNU Hurd
Versions: All versions before 0.9 20210404-9
Operating Systems: GNU Hurd
Default Config Vulnerable: ⚠️ Yes
Notes: Only affects GNU Hurd systems; not applicable to Linux, BSD, or other Unix-like systems.

📦 What is this software?

Hurd by Gnu

View all CVEs affecting Hurd →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Full system compromise with root privileges, allowing complete control over the operating system and all data.

🟠

Likely Case

Unauthorized file modification leading to privilege escalation and system takeover.

🟢

If Mitigated

Limited impact if systems are isolated or have strict access controls, but still vulnerable to privilege escalation.

🌐 Internet-Facing: LOW
🏢 Internal Only: HIGH

🎯 Exploit Status

Public PoC: ✅ No
Weaponized: UNKNOWN
Unauthenticated Exploit: ✅ No
Complexity: LOW

Exploitation requires local user access but is described as trivial once access is obtained.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 0.9 20210404-9 and later

Vendor Advisory: https://lists.gnu.org/archive/html/bug-hurd/2021-05/msg00079.html

Restart Required: Yes

Instructions:

1. Update GNU Hurd to version 0.9 20210404-9 or later. 2. Reboot the system to apply the kernel changes.

🔧 Temporary Workarounds

No effective workarounds

all

This is a kernel-level vulnerability requiring patching; no configuration changes can mitigate it.

🧯 If You Can't Patch

  • Isolate affected systems from network access and restrict user privileges to minimal levels.
  • Monitor for suspicious file modification activities and implement strict access controls.

🔍 How to Verify

Check if Vulnerable:

Check GNU Hurd version with 'uname -a' or system documentation; if version is earlier than 0.9 20210404-9, it is vulnerable.

Check Version:

uname -a

Verify Fix Applied:

After update, verify version is 0.9 20210404-9 or later using 'uname -a'.

📡 Detection & Monitoring

Log Indicators:

  • Unexpected file modifications by non-privileged users
  • Privilege escalation attempts in system logs

Network Indicators:

  • Not applicable as this is a local exploit

SIEM Query:

Search for events where non-root users modify system files or gain root privileges unexpectedly.

📊 Metadata

CVE ID: CVE-2021-43413
CVSS v3 Score: 8.8 (HIGH)
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published: November 7, 2021
Last Updated: November 21, 2024

🔗 References

📤 Share & Export

📄 Export Markdown 📋 Export JSON