CWE-775 Variant Incomplete

Missing Release of File Descriptor or Handle after Effective Lifetime

This vulnerability occurs when a program fails to properly close file descriptors or handles after they are no longer needed, leaving these system resources allocated.

Definition

What is CWE-775?

This vulnerability occurs when a program fails to properly close file descriptors or handles after they are no longer needed, leaving these system resources allocated.
File descriptors and handles are limited system resources that act as references to open files, network connections, or other I/O objects. When developers don't explicitly release them by calling close() or similar cleanup functions, these resources remain locked—even after the program stops using them. This creates a resource leak that accumulates over time, especially in long-running applications or loops. Attackers can exploit this weakness by repeatedly triggering the leak, eventually exhausting all available file descriptors on the system. This leads to a denial-of-service condition where legitimate processes—including the operating system itself—cannot open new files or network connections. The impact ranges from application crashes to full system instability, making proper resource lifecycle management essential for robust software.
Real-world impact

Real-world CVEs caused by CWE-775

  • CVE-2007-0897

    Chain: anti-virus product encounters a malformed file but returns from a function without closing a file descriptor (CWE-775) leading to file descriptor consumption (CWE-400) and failed scans.

How attackers exploit it

Step-by-step attacker path

  1. 1

    Identify a code path that handles untrusted input without validation.

  2. 2

    Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.

  3. 3

    Deliver the payload through a normal request and observe the application's reaction.

  4. 4

    Iterate until the response leaks data, executes attacker code, or escalates privileges.

Vulnerable code example

Vulnerable pseudo

MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.

Vulnerable pseudo 
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}
Secure code example

Secure pseudo

Secure pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist

How to prevent CWE-775

  • Operation / Architecture and Design Use resource-limiting settings provided by the operating system or environment. For example, when managing system resources in POSIX, setrlimit() can be used to set limits for certain types of resources, and getrlimit() can determine how many resources are available. However, these functions are not available on all operating systems. When the current levels get close to the maximum that is defined for the application (see CWE-770), then limit the allocation of further resources to privileged users; alternately, begin releasing resources for less-privileged users. While this mitigation may protect the system from attack, it will not necessarily stop attackers from adversely impacting other users. Ensure that the application performs the appropriate error checks and error handling in case resources become unavailable (CWE-703).
Detection signals

How to detect CWE-775

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

Plexicus auto-fix

Plexicus auto-detects CWE-775 and opens a fix PR in under 60 seconds.

Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.

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Frequently asked questions

Frequently asked questions

What is CWE-775?

This vulnerability occurs when a program fails to properly close file descriptors or handles after they are no longer needed, leaving these system resources allocated.

How serious is CWE-775?

MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.

What languages or platforms are affected by CWE-775?

MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.

How can I prevent CWE-775?

Use resource-limiting settings provided by the operating system or environment. For example, when managing system resources in POSIX, setrlimit() can be used to set limits for certain types of resources, and getrlimit() can determine how many resources are available. However, these functions are not available on all operating systems. When the current levels get close to the maximum that is defined for the application (see CWE-770), then limit the allocation of further resources to privileged…

How does Plexicus detect and fix CWE-775?

Plexicus's SAST engine matches the data-flow signature for CWE-775 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.

Where can I learn more about CWE-775?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/775.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-775

CWE-772 Parent

Missing Release of Resource after Effective Lifetime

This vulnerability occurs when a program fails to properly release a system resource—like memory, file handles, or network sockets—after…

CWE-1091 Sibling

Use of Object without Invoking Destructor Method

This weakness occurs when a program accesses an object but fails to properly call its destructor or finalizer method. This leaves the…

CWE-401 Sibling

Missing Release of Memory after Effective Lifetime

This vulnerability occurs when a program allocates memory but fails to properly release it after it's no longer needed, causing a gradual…

Resources

Further reading

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