Executive Summary

CVE-2026-26514 is an Argument Injection vulnerability in the traceroute module of the bird-lg-go project before a specific commit. The vulnerability arises because the module uses shlex.Split to parse user input without proper validation, allowing remote attackers to inject arbitrary command-line flags such as -w (timeout wait) and -q (number of probes) via the q parameter.

Attackers can exploit this flaw by injecting these flags along with an unreachable IP address, causing the traceroute process to hang for extended periods. This bypasses administrator-configured timeout and probe limits, leading to resource exhaustion on the server, such as excessive process IDs or memory consumption, ultimately resulting in a remote Denial of Service (DoS).

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Impact Analysis

This vulnerability can impact you by allowing remote attackers to cause a Denial of Service (DoS) on your system running bird-lg-go. By injecting arbitrary flags into the traceroute command, attackers can force the traceroute process to hang and consume excessive system resources such as CPU, memory, and process IDs.

This resource exhaustion can degrade system performance, make the service unavailable to legitimate users, and potentially cause system instability or crashes.

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Compliance Impact

I don't know

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Detection Guidance

This vulnerability can be detected by monitoring for unusual traceroute commands that include injected flags such as -w, -q, or -m, especially when combined with unreachable IP addresses like 192.0.2.1. An example of a suspicious traceroute command is: traceroute 192.0.2.1 -w 60 -q 10 -m 50.

To detect exploitation attempts on your system, you can look for traceroute processes that hang or run longer than expected, consuming excessive system resources such as CPU or memory.

Suggested commands to help detect this include:

• Use process monitoring tools like `ps aux | grep traceroute` to identify traceroute processes running unusually long.
• Use `top` or `htop` to monitor system resource usage and identify traceroute processes consuming excessive CPU or memory.
• Check network logs or proxy logs for traceroute requests containing suspicious parameters such as `-w`, `-q`, or `-m` flags.
• Use network monitoring tools to detect repeated traceroute requests targeting unreachable IPs with injected flags.

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Mitigation Strategies

Immediate mitigation steps include limiting the number of concurrent traceroute requests to prevent resource exhaustion and denial of service.

Specifically, update the bird-lg-go application to include the concurrency limit feature introduced in the patch for this vulnerability.

• Configure the `traceroute_max_concurrent` parameter to a reasonable number (default is 10) to restrict the maximum number of simultaneous traceroute executions.
• Ensure the application uses the semaphore mechanism to reject excess traceroute requests with an HTTP 503 status, protecting system resources.
• Monitor and update the bird-lg-go proxy component to the latest commit that includes these fixes (commit 6187a4e).

Additionally, consider validating and sanitizing user input to the traceroute module to prevent injection of arbitrary flags.

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