CWE-1265: Unintended Reentrant Invocation of Non-reentrant Code Via Nested Calls

CWE-1265: Unintended Reentrant Invocation of Non-reentrant Code Via Nested Calls is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product invokes code that is believed to be reentrant, but the code performs a call that unintentionally produces a nested invocation of the non-reentrant code. In a complex product, a single function call may lead to many different possible code paths, some of which may involve deeply nested calls. It may be difficult to foresee all possible code paths that could emanate from a given function call, even if that call is assumed to be reentrant. In some systems, an external actor can manipulate inputs to the system and thereby achieve a wide range of possible control flows. This is frequently a concern in products that execute scripts from untrusted sources. Examples of such products are web browsers and PDF readers. A weakness is present when one of the possible code paths resulting from a function call alters program state that the original caller assumes to be unchanged during the call.

If exploited, CWE-1265 (Unintended Reentrant Invocation of Non-reentrant Code Via Nested Calls) it can compromise Integrity, leading to outcomes such as Unexpected State.

Recommended mitigations for CWE-1265 include: When architecting a system that will execute untrusted code in response to events, consider executing the untrusted event handlers asynchronously (asynchronous message passing) as opposed to executing them synchronously at the time each event fires. The untrusted code should execute at the start of the next iteration of the thread's message loop. In this way, calls into non-reentrant code are strictly serialized, so that each operation completes fully before the next operation begins. Special attention must be paid to all places where type coercion may result in script execution. Performing all needed coercions at the very beginning of an operation can help reduce the chance of operations executing at unexpected junctures. Make sure the code (e.g., function or class) in question is reentrant by not leveraging non-local data, not modifying its own code, and not calling other non-reentrant code.

CWE-1265 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

MITRE documents real CVEs mapped to CWE-1265, including CVE-2014-1772 and CVE-2018-8174. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

A CWE (Common Weakness Enumeration) like CWE-1265 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.