CWE-617 Base Draft

Reachable Assertion

A reachable assertion occurs when an attacker can trigger an assert() statement or similar debugging check, causing the application to crash or behave in a more disruptive way than intended. This…

Definition

What is CWE-617?

A reachable assertion occurs when an attacker can trigger an assert() statement or similar debugging check, causing the application to crash or behave in a more disruptive way than intended. This turns a helpful development tool into a denial-of-service vulnerability.
Assertions are meant to catch logic errors during development, but if left in production code, they can be weaponized. An attacker who discovers the trigger condition can force the application to exit abruptly, disrupting service for all users. For instance, a single triggered assert() in a multi-connection server could terminate every active connection, causing widespread outage. While SAST tools can flag the presence of assertions, managing this risk at scale across a large codebase is challenging. An ASPM platform like Plexicus helps by continuously tracking these flaws in production, and its AI can recommend specific fixes—such as replacing the assert with proper error handling—saving significant manual remediation time.
Real-world impact

Real-world CVEs caused by CWE-617

  • CVE-2023-49286

    Chain: function in web caching proxy does not correctly check a return value (CWE-253) leading to a reachable assertion (CWE-617)

  • CVE-2006-6767

    FTP server allows remote attackers to cause a denial of service (daemon abort) via crafted commands which trigger an assertion failure.

  • CVE-2006-6811

    Chat client allows remote attackers to cause a denial of service (crash) via a long message string when connecting to a server, which causes an assertion failure.

  • CVE-2006-5779

    Product allows remote attackers to cause a denial of service (daemon crash) via LDAP BIND requests with long authcid names, which triggers an assertion failure.

  • CVE-2006-4095

    Product allows remote attackers to cause a denial of service (crash) via certain queries, which cause an assertion failure.

  • CVE-2006-4574

    Chain: security monitoring product has an off-by-one error that leads to unexpected length values, triggering an assertion.

  • CVE-2004-0270

    Anti-virus product has assert error when line length is non-numeric.

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 Java

In the excerpt below, an AssertionError (an unchecked exception) is thrown if the user hasn't entered an email address in an HTML form.

Vulnerable Java 
String email = request.getParameter("email_address");
  assert email != null;
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-617

  • Implementation Make sensitive open/close operation non reachable by directly user-controlled data (e.g. open/close resources)
  • Implementation Perform input validation on user data.
Detection signals

How to detect CWE-617

Automated Static Analysis High

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Plexicus auto-fix

Plexicus auto-detects CWE-617 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-617?

A reachable assertion occurs when an attacker can trigger an assert() statement or similar debugging check, causing the application to crash or behave in a more disruptive way than intended. This turns a helpful development tool into a denial-of-service vulnerability.

How serious is CWE-617?

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-617?

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

How can I prevent CWE-617?

Make sensitive open/close operation non reachable by directly user-controlled data (e.g. open/close resources) Perform input validation on user data.

How does Plexicus detect and fix CWE-617?

Plexicus's SAST engine matches the data-flow signature for CWE-617 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-617?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/617.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-617

CWE-670 Parent

Always-Incorrect Control Flow Implementation

This weakness occurs when a section of code is structured in a way that always executes incorrectly, regardless of input or conditions.…

CWE-480 Sibling

Use of Incorrect Operator

This vulnerability occurs when a developer mistakenly uses the wrong operator in their code, leading to unintended and potentially…

CWE-483 Sibling

Incorrect Block Delimitation

This vulnerability occurs when a developer fails to use explicit braces or delimiters to group multiple statements within a block, leading…

CWE-484 Sibling

Omitted Break Statement in Switch

This vulnerability occurs when a developer forgets to include a 'break' statement inside a switch-case block. Without it, the code…

CWE-698 Sibling

Execution After Redirect (EAR)

Execution After Redirect (EAR) occurs when a web application sends a redirect response to a user's browser but continues to run…

CWE-783 Sibling

Operator Precedence Logic Error

This vulnerability occurs when a developer writes a conditional expression where the intended logic is broken due to misunderstanding or…

Resources

Further reading

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