A 732-byte Python script is all it takes to obtain root privileges on millions of Linux systems affected by CVE-2026-31431, also known as Copy Fail. First disclosed by researchers at Theori and Xint in late April 2026, the vulnerability affects the Linux kernel’s authencesn cryptographic template.
Copy Fail affects virtually all Linux distributions running kernels released from 2017, placing enterprise servers, embedded systems, and other operational platforms within scope. But the real concern is not the size of the exploit. It is what Copy Fail reveals about modern Linux-based environments, where trusted kernel mechanisms can become pathways for full system compromise.
At a glance: Copy Fail
| Vulnerability | CVE-2026-31431 (Copy Fail) |
| CVSS score | 7.8 (High) |
| Vulnerability type | Local privilege escalation (AV:L/PR:L) |
| Attack vector | Local code execution by an unprivileged user (PR:L) |
| Brief technical description | A flaw in the Linux kernel’s crypto subsystem allows an attacker to corrupt the page cache of readable files, including setuid binaries. Attackers can abuse this behavior to execute code with root privileges and escalate access on affected systems. |
In a nutshell, Copy Fail allows an unprivileged local user to trigger a deterministic 4-byte overwrite within the Linux page cache, enabling modification of privileged binaries and escalation to root access on affected systems.
Unlike many privilege-escalation vulnerabilities that rely on race conditions or unstable memory corruption, Copy Fail enables a controlled, repeatable overwrite operation. This breaks an important security assumption within Linux systems: that read-only access to privileged files should not allow file modification.
Researchers demonstrated that attackers could modify setuid binaries and execute them with root privileges. Because the manipulation occurs within the Linux page cache rather than through conventional file writes, some traditional file integrity monitoring approaches may not immediately detect the change.
Is DirtyFrag another Copy Fail?
Within hours of public discussion surrounding Copy Fail, researchers disclosed another Linux local privilege escalation technique dubbed DirtyFrag, or “Copy Fail 2.”
According to researchers, DirtyFrag belongs to the same broader vulnerability class as Copy Fail, but affects a different Linux subsystem. Instead of targeting the Linux kernel’s authencesncryptographic template, it reportedly abuses Linux esp4, esp6, and rxrpc paths to achieve similar page-cache overwrite behavior and elevated privilege outcomes.
The rapid appearance of DirtyFrag suggests that researchers and attackers are now actively exploring a broader class of page-cache manipulation vulnerabilities across Linux subsystems. This shifts the conversation beyond a single vulnerability to deeper concerns about trusted kernel operations, copy-on-write assumptions, and filesystem memory-handling behavior.
At the time of writing, research surrounding DirtyFrag continues to evolve, including observations that similar behavior may also affect IPv6 processing paths.
Mapping Copy Fail and DirtyFrag to MITRE frameworks
VicOne’s CyberThreat Research Lab mapped publicly available exploitation methodologies to both the MITRE ATT&CK® and MITRE ATT&CK® for Automotive (ATM) frameworks to better understand how Copy Fail and DirtyFrag could integrate into broader attack chains across traditional enterprise and embedded automotive environments.
| Technical Action | MITRE Tactic | MITRE Technique (ID) | ATM Tactic | ATM Technique (ID) |
|---|---|---|---|---|
| Create a bash script | Resource Development | Develop Capabilities: Exploits (T1587.004) | N/A | N/A |
| Execute the Python script | Execution | Command and Scripting Interpreter: Python (T1059.006) | Execution | Command and Scripting Interpreter (ATM-T0018) |
| Send crafted payload via netlink | Privilege Escalation | Exploitation for Privilege Escalation (T1068) | Privilege Escalation | Exploit OS Vulnerability (ATM-T0026) |
| Execute /usr/bin/su for root | Privilege Escalation | Abuse Elevation Control Mechanism (T1548) | Privilege Escalation | Abuse Elevation Control Mechanism (ATM-T0024) |
Table 1. Copy Fail MITRE mapping
| Technical Action | MITRE Tactic | MITRE Technique (ID) | ATM Tactic | ATM Technique (ID) |
|---|---|---|---|---|
| Create a bash script | Resource Development | Develop Capabilities: Exploits (T1587.004) | N/A | N/A |
| Execute the bash script | Execution | Command and Scripting Interpreter: Unix Shell (T1059.004) | Execution | Command and Scripting Interpreter (ATM-T0018) |
| Bypass AppArmor | Defense Evasion | Abuse Elevation Control Mechanism (T1548) | Defense Evasion | Bypass Mandatory Access Control (ATM-T0034) |
| Access /etc/passwd | Discovery | File and Directory Discovery (T1083) | Discovery | File and Directory Discovery (ATM-T0042) |
| Send crafted UDP packet | Privilege Escalation | Exploitation for Privilege Escalation (T1068) | Privilege Escalation | Exploit OS Vulnerability (ATM-T0026) |
| Inject uid-0 user | Persistence | Create Account: Local Account (T1136.001) | N/A | N/A |
| Run su to obtain root | Privilege Escalation | Abuse Elevation Control Mechanism (T1548) | Privilege Escalation | Abuse Elevation Control Mechanism (ATM-T0024) |
Table 2. DirtyFrag (“Copy Fail 2”) MITRE mapping
The implications of these attack paths become increasingly significant as Linux-based software environments expand across modern vehicle architectures.
Why automotive OEMs should care
Modern vehicles rely heavily on Linux-based systems, including Automotive Grade Linux (AGL), AUTOSAR Adaptive platform, telematics systems, ADAS, gateways, and infotainment (IVI) environments. Copy Fail and DirtyFrag are significant because they demonstrate privilege-escalation techniques that bypass expected security boundaries and integrity protections in such embedded environments.
Key automotive cybersecurity concerns include:
- Container escape: If attackers gain limited access to an application or containerized environment, these vulnerabilities could allow them to escape from sandboxed execution environments and obtain elevated access to the underlying host operating system.
- Privilege escalation and lateral movement. Once elevated privileges are obtained within Linux-based automotive environments, attackers may be able to move laterally across connected systems, including gateways or Telematics Control Units (TCUs), depending on network segmentation, architecture, and existing security controls. In some scenarios, this could increase exposure to in-vehicle networks such as the CAN bus.
The deterministic nature of Copy Fail and DirtyFrag further increases their operational significance. Unlike vulnerabilities that rely on unstable race conditions or probabilistic memory corruption, these exploits demonstrate reliable and repeatable behavior, making them more practical for real-world weaponization once initial system access is achieved.
For automotive OEMs and suppliers, this reinforces the importance of rapid patch management, runtime monitoring, and behavioral detection alongside compliance efforts such as the Cyber Resilience Act (CRA) and ISO/SAE 21434.
What must be done next
Automotive OEMs and suppliers should prioritize patch validation, runtime monitoring, and behavioral detection for Linux-based and containerized automotive environments affected by Copy Fail and DirtyFrag. As exploit variants continue to emerge across Linux subsystems, defenders may need to move beyond static signatures and focus on detecting abnormal privilege escalation and syscall behavior associated with exploitation attempts.
Analysis conducted by VicOne’s CyberThreat Research Lab suggests that exploitation attempts associated with Copy Fail and DirtyFrag may result in highly anomalous behavior within electronic control units (ECUs) and embedded Linux deployments, where the legitimate use of certain kernel subsystems and networking paths is often limited or nonexistent.
This creates opportunities for high-confidence behavioral detection within constrained automotive environments. Frictionless IDS/IPS solutions such as VicOne xCarbon support this approach by enabling visibility into abnormal process execution and syscall behavior across Linux-based automotive and embedded systems.
As modern vehicles increasingly inherit the complexity of general-purpose computing platforms, vulnerabilities such as Copy Fail and DirtyFrag highlight how low-level kernel behaviors can become operationally significant risks within connected automotive ecosystems.