CWE-923 Class Incomplete

Improper Restriction of Communication Channel to Intended Endpoints

This vulnerability occurs when a system opens a communication channel for a sensitive task but fails to properly verify that it's actually talking to the correct, intended destination. This allows a…

Definition

What is CWE-923?

This vulnerability occurs when a system opens a communication channel for a sensitive task but fails to properly verify that it's actually talking to the correct, intended destination. This allows a malicious actor to impersonate the legitimate endpoint.
Attackers can exploit this flaw by spoofing or redirecting the connection to a system they control. Once they successfully impersonate the intended endpoint, they gain the same level of access and privileges, potentially leading to data theft, unauthorized actions, or full system compromise. While this commonly affects client-server authentication over networks, the core issue applies to any communication channel. This includes inter-process communication (IPC), cloud service APIs, container orchestration, and device-to-device links, wherever a trusted endpoint is assumed but not rigorously confirmed.
Real-world impact

Real-world CVEs caused by CWE-923

  • CVE-2022-30319

    S-bus functionality in a home automation product performs access control using an IP allowlist, which can be bypassed by a forged IP address.

  • CVE-2022-22547

    A troubleshooting tool exposes a web server on a random port between 9000-65535 that could be used for information gathering

  • CVE-2022-4390

    A WAN interface on a router has firewall restrictions enabled for IPv4, but it does not for IPv6, which is enabled by default

  • CVE-2012-2292

    Product has a Silverlight cross-domain policy that does not restrict access to another application, which allows remote attackers to bypass the Same Origin Policy.

  • CVE-2012-5810

    Mobile banking application does not verify hostname, leading to financial loss.

  • CVE-2014-1266

    chain: incorrect "goto" in Apple SSL product bypasses certificate validation, allowing Adversry-in-the-Middle (AITM) attack (Apple "goto fail" bug). CWE-705 (Incorrect Control Flow Scoping) -> CWE-561 (Dead Code) -> CWE-295 (Improper Certificate Validation) -> CWE-393 (Return of Wrong Status Code) -> CWE-300 (Channel Accessible by Non-Endpoint).

  • CVE-2000-1218

    DNS server can accept DNS updates from hosts that it did not query, leading to cache poisoning

How attackers exploit it

Step-by-step attacker path

  1. 1

    These cross-domain policy files mean to allow Flash and Silverlight applications hosted on other domains to access its data:

  2. 2

    Flash crossdomain.xml :

  3. 3

    Silverlight clientaccesspolicy.xml :

  4. 4

    These entries are far too permissive, allowing any Flash or Silverlight application to send requests. A malicious application hosted on any other web site will be able to send requests on behalf of any user tricked into executing it.

  5. 5

    This Android application will remove a user account when it receives an intent to do so:

Vulnerable code example

Vulnerable XML

Flash crossdomain.xml :

Vulnerable XML 
<cross-domain-policy xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:noNamespaceSchemaLocation="http://www.adobe.com/xml/schemas/PolicyFile.xsd">
  <allow-access-from domain="*.example.com"/>
  <allow-access-from domain="*"/>
  </cross-domain-policy>
Secure code example

Secure pseudo

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-923

  • 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-923

Automated Static Analysis High

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.)

Plexicus auto-fix

Plexicus auto-detects CWE-923 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-923?

This vulnerability occurs when a system opens a communication channel for a sensitive task but fails to properly verify that it's actually talking to the correct, intended destination. This allows a malicious actor to impersonate the legitimate endpoint.

How serious is CWE-923?

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-923?

MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.

How can I prevent CWE-923?

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-923?

Plexicus's SAST engine matches the data-flow signature for CWE-923 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-923?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/923.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-923

CWE-284 Parent

Improper Access Control

The software fails to properly limit who can access a resource, allowing unauthorized users or systems to interact with it.

CWE-1191 Sibling

On-Chip Debug and Test Interface With Improper Access Control

This vulnerability occurs when a hardware chip's debug or test interface (like JTAG) lacks proper access controls. Without correct…

CWE-1220 Sibling

Insufficient Granularity of Access Control

This vulnerability occurs when a system's access controls are too broad, allowing unauthorized users or processes to read or modify…

CWE-1224 Sibling

Improper Restriction of Write-Once Bit Fields

This vulnerability occurs when hardware write-once protection mechanisms, often called 'sticky bits,' are incorrectly implemented,…

CWE-1231 Sibling

Improper Prevention of Lock Bit Modification

This vulnerability occurs when hardware or firmware uses a lock bit to protect critical system registers or memory regions, but fails to…

CWE-1233 Sibling

Security-Sensitive Hardware Controls with Missing Lock Bit Protection

This vulnerability occurs when a hardware device uses a lock bit to protect critical configuration registers, but the lock fails to…

CWE-1252 Sibling

CPU Hardware Not Configured to Support Exclusivity of Write and Execute Operations

This vulnerability occurs when a CPU's hardware is not set up to enforce a strict separation between writing data to memory and executing…

CWE-1257 Sibling

Improper Access Control Applied to Mirrored or Aliased Memory Regions

This vulnerability occurs when a hardware design maps the same physical memory to multiple addresses (aliasing or mirroring) but fails to…

CWE-1259 Sibling

Improper Restriction of Security Token Assignment

This vulnerability occurs when a System-on-a-Chip (SoC) fails to properly secure its Security Token mechanism. These tokens control which…

Resources

Further reading

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