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-823 Base Incomplete
Use of Out-of-range Pointer Offset
This vulnerability occurs when a program calculates a new memory address using a valid pointer and an offset, but the resulting address points outside the intended, safe memory region, such as…
Definition
What is CWE-823?
This vulnerability occurs when a program calculates a new memory address using a valid pointer and an offset, but the resulting address points outside the intended, safe memory region, such as beyond the bounds of an array or structure.
Pointers are designed to reference memory, but software logic typically expects them to operate within specific boundaries, like an array's allocated space. When an offset—often from user input, a miscalculation, or corrupted data—pushes the pointer beyond these boundaries, it can read or write to arbitrary, unintended memory locations.
An attacker who controls this offset can exploit this to leak sensitive data, corrupt critical program variables, crash the application, or potentially execute malicious code. The core issue is a failure to properly validate that the pointer arithmetic result remains within the legitimate range of the target data structure before it is used.
Real-world impact
Real-world CVEs caused by CWE-823
-
Invalid offset in undocumented opcode leads to memory corruption.
-
Multimedia player uses untrusted value from a file when using file-pointer calculations.
-
Spreadsheet program processes a record with an invalid size field, which is later used as an offset.
-
Instant messaging library does not validate an offset value specified in a packet.
-
Language interpreter does not properly handle invalid offsets in JPEG image, leading to out-of-bounds memory access and crash.
-
negative offset leads to out-of-bounds read
-
untrusted offset in kernel
-
"blind trust" of an offset value while writing heap memory allows corruption of function pointer,leading to code execution
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 pseudo
MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
// Untrusted input flows directly into the sensitive sink.
return executeUnsafe(input);
} 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-823
- 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-823
Plexicus auto-detects CWE-823 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-823?
How serious is CWE-823?
What languages or platforms are affected by CWE-823?
How can I prevent CWE-823?
How does Plexicus detect and fix CWE-823?
Where can I learn more about CWE-823?
Frequently asked questions
What is CWE-823?
This vulnerability occurs when a program calculates a new memory address using a valid pointer and an offset, but the resulting address points outside the intended, safe memory region, such as beyond the bounds of an array or structure.
How serious is CWE-823?
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-823?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-823?
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-823?
Plexicus's SAST engine matches the data-flow signature for CWE-823 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-823?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/823.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-823
CWE-119 Parent
Improper Restriction of Operations within the Bounds of a Memory Buffer
This vulnerability occurs when software accesses a memory buffer but reads from or writes to a location outside its allocated boundary.…
CWE-120 Sibling
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
This vulnerability occurs when a program copies data from one memory location to another without first verifying that the source data will…
CWE-123 Sibling
Write-what-where Condition
A write-what-where condition occurs when an attacker can control both the data written and the exact memory location where it's written,…
CWE-125 Sibling
Out-of-bounds Read
An out-of-bounds read occurs when software accesses memory outside the boundaries of a buffer, array, or similar data structure, reading…
CWE-130 Sibling
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…
CWE-466 Sibling
Return of Pointer Value Outside of Expected Range
This vulnerability occurs when a function returns a memory pointer that points outside the expected buffer range, potentially exposing…
CWE-786 Sibling
Access of Memory Location Before Start of Buffer
This vulnerability occurs when software attempts to read from or write to a memory location positioned before the official start of a…
CWE-787 Sibling
Out-of-bounds Write
This vulnerability occurs when software incorrectly writes data outside the boundaries of its allocated memory buffer, either beyond the…
CWE-788 Sibling
Access of Memory Location After End of Buffer
This vulnerability occurs when software attempts to read from or write to a memory buffer using an index or pointer that points past the…
Ready when you are
Don't Let Security
Weigh You Down.
Stop choosing between AI velocity and security debt. Plexicus is the only platform that runs Vibe Coding Security and ASPM in parallel — one workflow, every codebase.