Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-1177 Class Incomplete
Use of Prohibited Code
This vulnerability occurs when software incorporates a function, library, or third-party component that has been explicitly banned by the development team or the customer.
Definition
What is CWE-1177?
This vulnerability occurs when software incorporates a function, library, or third-party component that has been explicitly banned by the development team or the customer.
Development teams or clients often create lists of prohibited code for critical reasons. These bans can stem from known security flaws, components that are notoriously hard to use safely, licensing conflicts, export control restrictions, reliance on obsolete or unmaintained code, or internal plans to phase out certain technologies. Ignoring these prohibitions directly introduces the specific risks the ban was meant to prevent.
Using banned functions or libraries increases security risk and maintenance costs. These components often have inherent weaknesses that can lead to exploits, and they may force developers to write complex, error-prone workarounds. Furthermore, they can create technical debt through compatibility issues, legal problems from license violations, and increased support overhead for code that the team has officially decided not to support.
Real-world impact
Real-world CVEs caused by CWE-1177
-
Library has multiple buffer overflows using sprintf() and strcpy()
-
FTP client uses inherently insecure gets() function and is setuid root on some systems, allowing buffer overflow
How attackers exploit it
Step-by-step attacker path
- 1
The code below calls the gets() function to read in data from the command line.
- 2
However, gets() is inherently unsafe, because it copies all input from STDIN to the buffer without checking size. This allows the user to provide a string that is larger than the buffer size, resulting in an overflow condition.
- 3
The following code attempts to create a local copy of a buffer to perform some manipulations to the data.
- 4
However, the programmer does not ensure that the size of the data pointed to by string will fit in the local buffer and copies the data with the potentially dangerous strcpy() function. This may result in a buffer overflow condition if an attacker can influence the contents of the string parameter.
Vulnerable code example
Vulnerable C
The code below calls the gets() function to read in data from the command line.
char buf[24];
printf("Please enter your name and press <Enter>\n");
gets(buf);
...
} 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-1177
- Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
- Implementation Validate input at trust boundaries; use allowlists, not denylists.
- Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
- Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
- Operation Monitor logs for the runtime signals listed in the next section.
Detection signals
How to detect CWE-1177
Run dynamic application security testing against the live endpoint.
Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.
Code review: flag any new code that handles input from this surface without using the validated framework helpers.
CWE-1177
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-1177?
How serious is CWE-1177?
What languages or platforms are affected by CWE-1177?
How can I prevent CWE-1177?
How does Plexicus detect and fix CWE-1177?
Where can I learn more about CWE-1177?
Frequently asked questions
What is CWE-1177?
This vulnerability occurs when software incorporates a function, library, or third-party component that has been explicitly banned by the development team or the customer.
How serious is CWE-1177?
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-1177?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-1177?
Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.
How does Plexicus detect and fix CWE-1177?
Plexicus's SAST engine matches the data-flow signature for CWE-1177 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-1177?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/1177.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-1177
CWE-710 Parent
Improper Adherence to Coding Standards
This weakness occurs when developers don't consistently follow established coding standards and best practices, which can introduce…
CWE-1041 Sibling
Use of Redundant Code
This weakness occurs when a codebase contains identical or nearly identical logic duplicated across multiple functions, methods, or…
CWE-1044 Sibling
Architecture with Number of Horizontal Layers Outside of Expected Range
This occurs when a software system is built with either too many or too few distinct architectural layers, falling outside a recommended…
CWE-1048 Sibling
Invokable Control Element with Large Number of Outward Calls
This weakness occurs when a single function, method, or callable code block makes an excessively high number of calls to other objects or…
CWE-1059 Sibling
Insufficient Technical Documentation
This weakness occurs when a software or hardware product lacks comprehensive technical documentation. Missing or incomplete details about…
CWE-1061 Sibling
Insufficient Encapsulation
This weakness occurs when a software component exposes too much of its internal workings, such as data structures or implementation logic.…
CWE-1065 Sibling
Runtime Resource Management Control Element in a Component Built to Run on Application Servers
This weakness occurs when an application built to run on a managed application server bypasses the server's high-level APIs and instead…
CWE-1066 Sibling
Missing Serialization Control Element
This weakness occurs when a class or data structure is marked as serializable but lacks the required control methods to properly handle…
CWE-1068 Sibling
Inconsistency Between Implementation and Documented Design
This weakness occurs when the actual code implementation deviates from the intended design described in its official documentation,…
Resources
Further reading
- MITRE — official CWE-1177 https://cwe.mitre.org/data/definitions/1177.html
- Microsoft's Free Security Tools - banned.h https://www.microsoft.com/en-us/security/blog/2012/08/30/microsofts-free-security-tools-banned-h/
- Microsoft's Free Security Tools - banned.h https://www.microsoft.com/en-us/security/blog/2012/08/30/microsofts-free-security-tools-banned-h/
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