usually there are two pointers involved. One part of the code has its pointer and frees whatever it points at, then another part of the code uses its copy to access the now freed memory. If the first part sets its copy to NULL it doesn't change any other copies of the pointer that are somewhere else. Answer from aocregacc on reddit.com
Kaspersky IT Encyclopedia
encyclopedia.kaspersky.com › glossary › use-after-free
What is Use-After-Free? | Kaspersky IT Encyclopedia
February 18, 2026 - Use-After-Free (UAF) is a vulnerability related to incorrect use of dynamic memory during program operation.
MITRE
cwe.mitre.org › data › definitions › 416.html
CWE-416: Use After Free - Common Weakness Enumeration
Common Weakness Enumeration (CWE) is a list of software weaknesses.
Why is use after free error is so common?
usually there are two pointers involved. One part of the code has its pointer and frees whatever it points at, then another part of the code uses its copy to access the now freed memory. If the first part sets its copy to NULL it doesn't change any other copies of the pointer that are somewhere else. More on reddit.com
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May 25, 2025Automated Use-After-Free Detection and Exploit Mitigation: How Far Have We Gone
An interesting read. It is nice to see more and more safety focus being added by the C++ community. This was seriously lacking ~2005->2015 and shows in many middleware libraries today. Many still refuse to use *any* smart pointer library, let alone that introduced to std ~C++0x / TR1. Even something as minimal as the following is very difficult to detect with static analysis and yet could easily result in a use-after-free. void Bomb::explode(std::shared_ptr& _self) { _self = std::make_shared(); m_name = "Booom"; } 99% of these issues could be mitigated if shared_ptr operator -> and * would increase reference count for the duration of access. Same with vector operator[] and iterator. Obviously this would cause overhead in terms of atomic incrementing ref count. However it would *still* be potentially faster than Java / CSharp.NET so whilst it wont replace high performance C++, it could replace switching language entirely. The fact that the OP paper even mentions Rust as upcoming shows that C++ has some rough edges in this regard. More on reddit.com
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October 27, 2021An Introduction to Use After Free Vulnerabilities
It's sad the site is unusable on phone :/
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August 8, 2016Zenbleed Write-up: New use-after-free exploit affecting all AMD Zen 2 CPUs.
AMD's current mitigation is to set the (controversially named) chicken bit to DE_CFG[9].
AMD has patched the microcode for only the EPYC 7002 series. The remaining datacenter CPUs are expected to be patched in October, whereas consumer CPUs will be vulnerable until December (source).
As a sidenote, this exploit is not really comparable to Spectre. While both involved speculative execution, Spectre was a design flaw in the entire concept of speculative execution whereas this appears to be a very specific set of misbehaving instructions.
More on reddit.com 46
284
July 28, 2023What is the best way to prevent use-after-free bugs in new software?
Adopt memory-safe languages, use strict code review processes, rely on automated analysis tools, and keep all dependencies up to date.
huntress.com
huntress.com › cybersecurity-101 › topic › what-is-use-after-free
Use-After-Free Explained: Master the Basics and Stay Secure | Huntress
Which software is most affected by use-after-free bugs?
Web browsers (Chrome, Firefox, Safari, Edge), operating system kernels (Windows, Linux), and applications written in C or C++ are the most frequently affected. Any software that manages memory manually is at risk.
automox.com
automox.com › blog › vulnerability-definition-use-after-free
What Is a Use-After-Free Vulnerability? | Automox
How serious are use-after-free vulnerabilities?
Very serious. MITRE ranked use-after-free as the fourth most dangerous software weakness in 2024. These vulnerabilities frequently lead to remote code execution with elevated privileges, making them high-priority targets for both attackers and patch management teams.
automox.com
automox.com › blog › vulnerability-definition-use-after-free
What Is a Use-After-Free Vulnerability? | Automox
Videos
14:59
Use After Free Vulnerabilities Demystified - YouTube
12:33
Physical Use-After-Free in the iOS Kernel (PhysPuppet) - YouTube
10:59
Introduction to Use-After-Free Vulnerabilities | UserAfterFree ...
36:09
Understanding & explaining Use-After-Free vulnerability, a critical ...
17:30
Exploiting a Use-After-Free (UAF) Vulnerability - "Unsubscriptions ...
47:13
Use After Free Exploitation - YouTube
Huntress
huntress.com › cybersecurity-101 › topic › what-is-use-after-free
Use-After-Free Explained: Master the Basics and Stay Secure | Huntress
Once it’s done, it’s supposed to "check out" and release the memory (freeing it). But if the software forgets to erase all references to that memory, it might try to use it again later = disaster. ... After memory is freed, the pointer still points to the old address.
OWASP Foundation
owasp.org › www-community › vulnerabilities › Using_freed_memory
Using freed memory | OWASP Foundation
The simplest way data corruption may occur involves the system’s reuse of the freed memory. In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed.
Snyk Learn
learn.snyk.io › home › security education › use after free vulnerability | tutorial & examples
Use after free vulnerability | Tutorial & Examples | Snyk Learn
September 28, 2023 - In this lesson, you will learn how use after free (UAF) bugs works and how to protect your applications against them. We will begin by exploiting a UAF vulnerability in a simple ticketing application.
Automox
automox.com › blog › vulnerability-definition-use-after-free
What Is a Use-After-Free Vulnerability? | Automox
A use-after-free vulnerability happens when a program tries to use a piece of memory after it has already been released. It's like returning a library book but still trying to read the pages that now belong to someone else's checkout.
Reddit
reddit.com › r/c_programming › why is use after free error is so common?
r/C_Programming on Reddit: Why is use after free error is so common?
May 25, 2025 -
Whenever I hear about a software vulnerability, most of the time it comes down to use after free. Why is it so? Doesn't setting the pointer to NULL would solve this problem? Here's a macro I wrote in 5mins on my phone that I believe would solve the issue and spot this vulnerability in debug build
#if DEBUG
#define NIL ((void*)0xFFFFFFFFFFFFFFFFUL)
#else
#define NIL ((void *)0)
#endif
#define FREE(BLOCK) do { \
#if DEBUG \
if (BLOCK == NIL) { \
/* log the error, filename, linenumber, etc... and exit the program */ \
} \
#endif \
free(BLOCK); \
BLOCK = NIL; \
} while (0)Is this approach bad? Or why something like this isn't done?
If this post is stupid and/or if I'm missing something, please go easy on me.
P.S. A while after posting this, I just realised that I was confusing use after free with double freeing memory. My bad
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usually there are two pointers involved. One part of the code has its pointer and frees whatever it points at, then another part of the code uses its copy to access the now freed memory. If the first part sets its copy to NULL it doesn't change any other copies of the pointer that are somewhere else.
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The problem comes when you have more than one reference to an object, you call free on one of those references, set it to NULL and it’s all good, but you don’t have any way to find, or even know, what the other references could be that still point to the now freed object.
White Knight Labs
whiteknightlabs.com › 2025 › 06 › 03 › understanding-use-after-free-uaf-in-windows-kernel-drivers
Understanding Use-After-Free (UAF) in Windows Kernel Drivers | White Knight Labs
June 3, 2025 - This PoC demonstrates a use-after-free (UAF) vulnerability in a kernel driver. It opens the vulnerable device and sends an IOCTL command (IOCTL_TEST_CODE) that triggers the UAF. The driver attempts to access memory (wrenchData) that has already been freed, leading to invalid memory access, which could cause memory corruption, system instability, or a BSOD.
Luk6xff
luk6xff.github.io › other › safe_secure_rust_book › memory_safety › use_after_free.html
Use After Free - Safe and Secure Coding in Rust: A Comparative Analysis of Rust and C/C++
fn main() { let ptr = Box::new(10); // Memory is automatically cleaned up when `ptr` goes out of scope // Attempting to use `ptr` after this point would result in a compile-time error println!("{}", ptr); // Rust's ownership system prevents "use after free" by design }
Medium
expl0it32.medium.com › demystifying-use-after-free-vulnerabilities-a-deep-dive-into-memory-safety-issues-78ee7f8d44c2
Demystifying Use-After-Free Vulnerabilities: A Deep Dive into Memory Safety Issues | by eXpl0it_32 | Medium
April 23, 2025 - A Use-After-Free (UAF) vulnerability arises when a program continues to access memory that has already been deallocated (freed). This happens in low-level languages like C or C++, where developers are responsible for managing memory manually.
Black Hat
blackhat.com › docs › eu-16 › materials › eu-16-Wen-Use-After-Use-After-Free-Exploit-UAF-By-Generating-Your-Own-wp.pdf pdf
Use-After-Use-After-Free: Exploit UAF by Generating Your Own Guanxing Wen
creates memory holes by freeing some Vectors. Vulnerable buffer is created to occupy one of the memory · holes, corrupting the length field of a Vector object by triggering an overflow. A Vector with a large · length is then utilized to search the process memory for ROP gadgets.
Red Hat
access.redhat.com › articles › use-after-free-flaw-type
What is a use after free ? - Red Hat Customer Portal
For example, if executable instructions to exist in this free'd area an attacker may be able to replace it with a GIF image. This GIF image may be invalid as a GIF file, but valid executable code. When the system attempts to execute this new code it will then run the attackers functionality, not the previous code that had existed before. The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw.
Forbes
forbes.com › sites › daveywinder › 2026 › 07 › 10 › google-confirms-new-and-critical-chrome-use-after-free-memory-update
Google Confirms New And Critical Chrome ‘Use-After-Free’ Memory Update
4 days ago - The Open Worldwide Application Security Project defines a use-after-free condition as something that happens when a program references heap-allocated memory after it has already been freed or deleted.
Medium
infosecwriteups.com › use-after-free-13544be5a921
The toddler’s introduction to Heap exploitation, Use After Free & Double free (Part 4)
February 1, 2023 - The attempt to use a chunk that has previously been freed is called “Use After Free” (UAF) and it is one of the most commonly encountered bugs with an impact varying from a simple program crash to arbitrary code execution.
CQR
cqr.company › web-vulnerabilities › use-after-free-vulnerability
Use-After-Free vulnerability | CQR
Vulnerability Assessment as a Service ... weaknesses. Learn More Use-After-Free is a type of memory vulnerability that occurs when a program continues to access memory that it has already freed. The term "Use-After-Free" refers ...
Linux Security
linuxsecurity.com › features › what-is-a-use-after-free-uaf-vulnerability
Use After Free Vulnerability in Linux Servers: Risks and Mitigation
August 14, 2025 - Ever wonder how a seemingly minor bug in memory management can crack open a door for attackers to slip through and compromise your Linux server? Meet the use after free (UAF) vulnerability—an elusive and dangerous class of memory corruption flaw that has plagued Linux systems (and others) ...
SensePost
sensepost.com › blog › 2017 › linux-heap-exploitation-intro-series-used-and-abused-use-after-free
SensePost | Linux Heap Exploitation Intro Series: Used and Abused – Use After Free
In human-readable language this means that at some point of the implementation there was a logic flaw that caused a free() on a chunk, but despite being free()’d, its memory position is still referenced, effectively making use of the free’d chunk’s data after it has been set free.
USENIX
usenix.org › conference › usenixsecurity21 › presentation › wickman
Preventing Use-After-Free Attacks with Fast Forward Allocation | USENIX
Memory-unsafe languages are widely used to implement critical systems like kernels and browsers, leading to thousands of memory safety issues every year. A use-after-free bug is a temporal memory error where the program accidentally visits a freed memory location.
NordVPN
nordvpn.com › cybersecurity › glossary › use-after-free
Use-after-free definition – Glossary | NordVPN
April 16, 2026 - Use-after-free is a type of memory corruption vulnerability that occurs when a program continues to use a memory location after it has been freed or deallocated. This can lead to unforeseen behavior, including crashes, data corruption, or the ...
6point6
6point6.co.uk › insights › common-software-vulnerabilities-part-ii-explaining-the-use-after-free
Delivering UK sovereign digital expertise where it matters | Accenture
We use the insights gained to ideate and define the optimal user experience, supporting business processes, technologies and secure infrastructure.