Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-130 Base Incomplete
Improper Handling of Length Parameter Inconsistency
This vulnerability occurs when a program reads a structured data packet or message but fails to properly validate that the declared length field matches the actual amount of data provided.
Definition
What is CWE-130?
This vulnerability occurs when a program reads a structured data packet or message but fails to properly validate that the declared length field matches the actual amount of data provided.
Attackers exploit this flaw by deliberately sending data where the stated length is incorrect—either longer or shorter than the real payload. This inconsistency tricks the application's parsing logic, often leading to catastrophic security failures like buffer overflows, memory corruption, or the processing of garbage data as if it were legitimate instructions.
In practice, an attacker might use a manipulated length field to inject massive amounts of data beyond allocated buffers or to carefully craft input that alters critical application state. The core defense is for developers to always independently calculate or strictly verify data lengths during parsing, never trusting the user-supplied length parameter alone before processing the associated data block.
Real-world impact
Real-world CVEs caused by CWE-130
-
Chain: "Heartbleed" bug receives an inconsistent length parameter (CWE-130) enabling an out-of-bounds read (CWE-126), returning memory that could include private cryptographic keys and other sensitive data.
-
Web application firewall consumes excessive memory when an HTTP request contains a large Content-Length value but no POST data.
-
Buffer overflow in internal string handling routine allows remote attackers to execute arbitrary commands via a length argument of zero or less, which disables the length check.
-
Web server allows remote attackers to cause a denial of service via an HTTP request with a content-length value that is larger than the size of the request, which prevents server from timing out the connection.
-
Service does not properly check the specified length of a cookie, which allows remote attackers to execute arbitrary commands via a buffer overflow, or brute force authentication by using a short cookie length.
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Traffic analyzer allows remote attackers to cause a denial of service and possibly execute arbitrary code via invalid IPv4 or IPv6 prefix lengths, possibly triggering a buffer overflow.
-
Chat client allows remote attackers to cause a denial of service or execute arbitrary commands via a JPEG image containing a comment with an illegal field length of 1.
-
Server allows remote attackers to cause a denial of service and possibly execute arbitrary code via a negative Content-Length HTTP header field causing a heap-based buffer overflow.
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 C
In the following C/C++ example the method processMessageFromSocket() will get a message from a socket, placed into a buffer, and will parse the contents of the buffer into a structure that contains the message length and the message body. A for loop is used to copy the message body into a local character string which will be passed to another method for processing.
int processMessageFromSocket(int socket) {
int success;
char buffer[BUFFER_SIZE];
char message[MESSAGE_SIZE];
```
// get message from socket and store into buffer*
*//Ignoring possibliity that buffer > BUFFER_SIZE*
if (getMessage(socket, buffer, BUFFER_SIZE) > 0) {
```
```
// place contents of the buffer into message structure*
ExMessage *msg = recastBuffer(buffer);
*// copy message body into string for processing*
int index;
for (index = 0; index < msg->msgLength; index++) {
```
message[index] = msg->msgBody[index];
}
message[index] = '\0';
```
// process message*
success = processMessage(message);}
return success;} 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-130
- Implementation When processing structured incoming data containing a size field followed by raw data, ensure that you identify and resolve any inconsistencies between the size field and the actual size of the data.
- Implementation Do not let the user control the size of the buffer.
- Implementation Validate that the length of the user-supplied data is consistent with the buffer size.
Detection signals
How to detect CWE-130
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.
Plexicus auto-detects CWE-130 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.
Frequently asked questions What is CWE-130?
How serious is CWE-130?
What languages or platforms are affected by CWE-130?
How can I prevent CWE-130?
How does Plexicus detect and fix CWE-130?
Where can I learn more about CWE-130?
Frequently asked questions
What is CWE-130?
This vulnerability occurs when a program reads a structured data packet or message but fails to properly validate that the declared length field matches the actual amount of data provided.
How serious is CWE-130?
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-130?
MITRE lists the following affected platforms: C, C++.
How can I prevent CWE-130?
When processing structured incoming data containing a size field followed by raw data, ensure that you identify and resolve any inconsistencies between the size field and the actual size of the data. Do not let the user control the size of the buffer.
How does Plexicus detect and fix CWE-130?
Plexicus's SAST engine matches the data-flow signature for CWE-130 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-130?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/130.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-130
CWE-240 Parent
Improper Handling of Inconsistent Structural Elements
This vulnerability occurs when a system fails to properly manage situations where related data structures or elements should match but are…
CWE-805 Can precede
Buffer Access with Incorrect Length Value
This vulnerability occurs when software reads from or writes to a buffer using a loop or sequential operation, but mistakenly calculates…
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