# CWE-476: NULL Pointer Dereference

**Likelihood of exploit:** Medium · **KEV-linked**

> As of 2026-10-05, CWE-476 (NULL Pointer Dereference) underlies 23 CVEs tracked by Threadlinqs, 1 of them in the CISA Known Exploited Vulnerabilities catalog, and is cited by 10 tracked threats. MITRE rates its likelihood of exploit as Medium.

**Last updated:** 2026-10-05

## What is CWE-476?

The product dereferences a pointer that it expects to be valid but is NULL.

CWE-476 is a base-level weakness in MITRE’s Common Weakness Enumeration, with a MITRE likelihood of exploit of Medium. Applicable platforms: Language: C; Language: C++; Language: Java; Language: C#; Language: Go.

_Source: [MITRE CWE](https://cwe.mitre.org/data/definitions/476.html) (CWE-476 definition, reproduced verbatim). Counts and linkage below are Threadlinqs data._

## Consequences

- **Availability** — DoS: Crash, Exit, or Restart. NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
- **Integrity, Confidentiality** — Execute Unauthorized Code or Commands, Read Memory, Modify Memory. In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.

_Source: MITRE CWE, common consequences._

## How CWE-476 is exploited in the wild

Threadlinqs maps 23 CVEs to CWE-476, published between 2019-05-15 and 2026-09-30. 1 is listed in CISA’s Known Exploited Vulnerabilities catalog, the authoritative record of exploitation in the wild. By CVSS v3 severity the set splits into 9 high, 10 medium. The highest EPSS score in the set is 11.7% (CVE-2026-21525), the modelled probability of exploitation in the next 30 days. 10 tracked threats reference CWE-476 directly or through a CVE it covers; the most recent is “WatchGuard Fireware OS Critical Code Injection Vulnerability in BOVPN over TLS Client (CVE-2026-86131)” (2026-09-30). Affected products concentrate in Miniupnp Project (3), Wireshark Foundation (3), zephyrproject (3), among 14 vendors in total.

## Vulnerabilities (CVEs)

All 23 CVEs mapped to CWE-476, CISA KEV first, then by CVSS score.

- [CVE-2026-21525](https://intel.threadlinqs.com/cve/CVE-2026-21525) — CISA KEV · CVSS 6.2 medium · EPSS 11.7% · published 2026-02-10
- [CVE-2019-12111](https://intel.threadlinqs.com/cve/CVE-2019-12111) — CVSS 7.5 high · EPSS 3.4% · published 2019-05-15
- [CVE-2019-12108](https://intel.threadlinqs.com/cve/CVE-2019-12108) — CVSS 7.5 high · EPSS 2.7% · published 2019-05-15
- [CVE-2019-12109](https://intel.threadlinqs.com/cve/CVE-2019-12109) — CVSS 7.5 high · EPSS 2.7% · published 2019-05-15
- [CVE-2019-12110](https://intel.threadlinqs.com/cve/CVE-2019-12110) — CVSS 7.5 high · EPSS 2.5% · published 2019-05-15
- [CVE-2026-15891](https://intel.threadlinqs.com/cve/CVE-2026-15891) — CVSS 7.5 high · EPSS 0.3% · published 2026-09-13
- [CVE-2026-76928](https://intel.threadlinqs.com/cve/CVE-2026-76928) — CVSS 7.5 high · EPSS 0.2% · published 2026-08-19
- [CVE-2025-56363](https://intel.threadlinqs.com/cve/CVE-2025-56363) — CVSS 7.5 high · EPSS 0.2% · published 2026-07-14
- [CVE-2026-58101](https://intel.threadlinqs.com/cve/CVE-2026-58101) — CVSS 7.5 high · EPSS 0.1% · published 2026-07-13
- [CVE-2026-55204](https://intel.threadlinqs.com/cve/CVE-2026-55204) — CVSS 7.5 high · published 2026-06-18
- [CVE-2026-10648](https://intel.threadlinqs.com/cve/CVE-2026-10648) — CVSS 6.2 medium · EPSS 0.1% · published 2026-06-29
- [CVE-2026-48985](https://intel.threadlinqs.com/cve/CVE-2026-48985) — CVSS 5.5 medium · published 2026-06-18
- [CVE-2026-76922](https://intel.threadlinqs.com/cve/CVE-2026-76922) — CVSS 5.5 medium · published 2026-08-19
- [CVE-2026-90485](https://intel.threadlinqs.com/cve/CVE-2026-90485) — CVSS 5.5 medium · published 2026-09-12
- [CVE-2026-90829](https://intel.threadlinqs.com/cve/CVE-2026-90829) — CVSS 5.3 medium · EPSS 0.1% · published 2026-09-14
- [CVE-2026-90830](https://intel.threadlinqs.com/cve/CVE-2026-90830) — CVSS 5.3 medium · EPSS 0.1% · published 2026-09-14
- [CVE-2026-76927](https://intel.threadlinqs.com/cve/CVE-2026-76927) — CVSS 4.7 medium · EPSS 0.1% · published 2026-08-19
- [CVE-2026-10656](https://intel.threadlinqs.com/cve/CVE-2026-10656) — CVSS 4.6 medium · EPSS 0.1% · published 2026-07-05
- [CVE-2026-82588](https://intel.threadlinqs.com/cve/CVE-2026-82588) — CVSS 4.3 medium · EPSS 0.3% · published 2026-08-30
- [CVE-2026-86134](https://intel.threadlinqs.com/cve/CVE-2026-86134) — EPSS 0.4% · published 2026-09-30
- [CVE-2025-66281](https://intel.threadlinqs.com/cve/CVE-2025-66281) — EPSS 0.3% · published 2026-06-10
- [CVE-2026-19026](https://intel.threadlinqs.com/cve/CVE-2026-19026) — EPSS 0.1% · published 2026-08-05
- [CVE-2026-19024](https://intel.threadlinqs.com/cve/CVE-2026-19024) — EPSS 0.1% · published 2026-08-05

## Affected vendors

- **Miniupnp Project** — 3 CVEs
- [Wireshark Foundation](https://intel.threadlinqs.com/vendors/wireshark-foundation) — 3 CVEs
- [zephyrproject](https://intel.threadlinqs.com/vendors/zephyrproject) — 3 CVEs
- [GNU](https://intel.threadlinqs.com/vendors/gnu) — 2 CVEs
- **The HDF Group** — 2 CVEs
- [Debian](https://intel.threadlinqs.com/vendors/debian) — 1 CVE
- **IOBit** — 1 CVE
- **JONASBN** — 1 CVE
- [Microsoft](https://intel.threadlinqs.com/vendors/microsoft) — 1 CVE
- **Miniupnp.free** — 1 CVE
- **QNAP Systems Inc.** — 1 CVE
- [WatchGuard](https://intel.threadlinqs.com/vendors/watchguard) — 1 CVE

## Threat activity

10 tracked threats cite CWE-476:

- [WatchGuard Fireware OS Critical Code Injection Vulnerability in BOVPN over TLS Client (CVE-2026-86131)](https://intel.threadlinqs.com/threat/TL-2026-2813) — CRITICAL · 2026-09-30
- [Adobe and Nvidia Patch Dozens of Vulnerabilities Across Multiple Products, Including Two Critical Flaws in Nvidia's NemoClaw AI Agent Stack and a CVSS 10.0 Adobe Campaign Classic Chain](https://intel.threadlinqs.com/threat/TL-2026-2152) — CRITICAL · 2026-08-26
- [Claude Mythos / Project Glasswing: Autonomous AI Vulnerability Discovery Compresses the Find-to-Exploit Timeline (CVE-2026-4747 and the AI-Scale Disclosure Problem)](https://intel.threadlinqs.com/threat/TL-2026-1253) — HIGH · 2026-07-13
- [VEXAIoT: Autonomous Multi-Agent LLM Framework Automates End-to-End IoT Vulnerability Discovery and Exploitation (95% Success Rate)](https://intel.threadlinqs.com/threat/TL-2026-1261) — MEDIUM · 2026-07-13
- [Six AirDrop and Quick Share Proximity File-Transfer Vulnerabilities (Apple, Google, Samsung) — 'Protocol Prying' Research](https://intel.threadlinqs.com/threat/TL-2026-1197) — MEDIUM · 2026-07-10
- [XZ Utils Multithreaded Decoder Race Condition (CVE-2025-31115) - B&R & Siemens ICS Impact](https://intel.threadlinqs.com/threat/TL-2026-1001) — HIGH · 2026-06-30
- [QNAP QSA-26-10: Multiple Injection and Memory-Safety Vulnerabilities in QTS, QuTS hero, QuTS cloud, QVP, and File Station (CVE-2025-66273, CVE-2026-26240, and 12 others)](https://intel.threadlinqs.com/threat/TL-2026-0901) — HIGH · 2026-06-22
- [Research: ~90% of Leaked Malware Source Code Contains Exploitable Software Weaknesses (Vouvoutsis, Patsakis & Casino, arXiv:2606.05945)](https://intel.threadlinqs.com/threat/TL-2026-0739) — INFO · 2026-06-09
- [February 2026 Patch Tuesday: Six Zero-Days Among 59 CVEs](https://intel.threadlinqs.com/threat/TL-2026-0064) — CRITICAL · 2026-02-12
- [February 2026 Patch Tuesday: Six Zero-Days Among 59 CVEs — CrowdStrike-Discovered RDP EoP Exploited Since December 2025](https://intel.threadlinqs.com/threat/TL-2026-0074) — CRITICAL · 2026-02-12

## Mitigations

- **Implementation**: For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished [REF-1484].
- **Requirements**: Select a programming language that is not susceptible to these issues.
- **Implementation**: Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
- **Architecture and Design**: Identify all variables and data stores that receive information from external sources, and apply input validation to make sure that they are only initialized to expected values.
- **Implementation**: Explicitly initialize all variables and other data stores, either during declaration or just before the first usage.

_Source: MITRE CWE, potential mitigations._

## Detection methods (MITRE CWE)

- **Automated Dynamic Analysis** (effectiveness: Moderate): This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
- **Manual Dynamic Analysis**: Identify error conditions that are not likely to occur during normal usage and trigger them. For example, run the program under low memory conditions, run with insufficient privileges or permissions, interrupt a transaction before it is completed, or disable connectivity to basic network services such as DNS. Monitor the software for any unexpected behavior. If you trigger an unhandled exception or similar error that was discovered and handled by the application's environment, it may still…
- **Automated Static Analysis** (effectiveness: 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.)
- **Automated Dynamic Analysis** (effectiveness: Moderate): Use tools that are integrated during compilation to insert runtime error-checking mechanisms related to memory safety errors, such as AddressSanitizer (ASan) for C/C++ [REF-1518].

_Source: MITRE CWE, detection methods. Threadlinqs detection rules for the threats above are Blue tier and higher._

## Related weaknesses

- [CWE-710](https://cwe.mitre.org/data/definitions/710.html)
- [CWE-754 Improper Check for Unusual or Exceptional Conditions](https://intel.threadlinqs.com/cwe/CWE-754)

Canonical: https://intel.threadlinqs.com/cwe/CWE-476
Source definition: https://cwe.mitre.org/data/definitions/476.html
Detection rules and IOCs for threats exploiting CWE-476 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp