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.)
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
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Chain: function in web caching proxy does not correctly check a return value (CWE-253) leading to a reachable assertion (CWE-617)
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FTP server allows remote attackers to cause a denial of service (daemon abort) via crafted commands which trigger an assertion failure.
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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.
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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.
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Product allows remote attackers to cause a denial of service (crash) via certain queries, which cause an assertion failure.
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Chain: security monitoring product has an off-by-one error that leads to unexpected length values, triggering an assertion.
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Anti-virus product has assert error when line length is non-numeric.
How attackers exploit it
Step-by-step attacker path
- 1
Identify a code path that handles untrusted input without validation.
- 2
Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.
- 3
Deliver the payload through a normal request and observe the application's reaction.
- 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.
String email = request.getParameter("email_address");
assert email != null; Secure code example
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
CWE-617
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Frequently asked questions What is CWE-617?
How serious is CWE-617?
What languages or platforms are affected by CWE-617?
How can I prevent CWE-617?
How does Plexicus detect and fix CWE-617?
Where can I learn more about CWE-617?
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…
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