- by x32x01 ||
A publicly released proof-of-concept called PrettyPrague exposed a serious privilege-escalation flaw in Avast's sandbox. The exploit was designed to abuse Avast's security boundary to access the Windows SAM database and ultimately obtain a shell running as
The PoC was published by the researcher known as Nightmare Eclipse, also associated with the names Chaotic Eclipse, Infinite Nightmare, and MSNightmare. Independent security researchers reported that the exploit works against updated Windows 11 systems with Avast installed.
There is an important update, though: Gen Digital has since acknowledged the vulnerability and stated that the issue has been fixed. Users should therefore make sure Avast is fully updated rather than assuming that the public PoC means every current installation remains vulnerable.
The basic security problem is a local privilege escalation. An attacker who can already execute code as a lower-privileged user may be able to abuse Avast's privileged components to reach resources that should normally be protected from that user.
According to the research surrounding the PoC, the attack can:
The live SAM database is normally protected from ordinary users. A standard process should not simply be able to open the file and read its contents.
An attacker who gains access to the SAM can potentially obtain valuable credential material for offline analysis and further attacks.
However, it is important to understand that the SAM does not simply contain your Windows password in plain text. Access to the database provides credential-related information, such as password hashes, rather than a readable list of everyone's actual passwords.
Instead of allowing suspicious software to interact freely with the operating system, the security product places the process inside an isolated environment and restricts what it can access.
Avast's sandbox uses privileged components, including a kernel driver, to provide this isolation.
That creates an important security boundary:
A normal user should not be able to use the antivirus's privileged components to gain more privileges.
PrettyPrague reportedly found a way to abuse that boundary.
Research into the PoC indicates that Avast's sandbox virtualization could cause a protected SAM-related file to appear in a location accessible from outside the sandbox. The exploit then monitors the sandbox environment and attempts to obtain the redirected copy before it is removed.
In other words, the sandbox itself becomes part of the attack path rather than providing the expected protection.
The important security issue is the boundary between the unprivileged user, the Avast sandbox, and the privileged Avast components.
A process running as
Depending on the environment, an attacker with SYSTEM-level execution could potentially:
Ironically, the security product itself becomes the mechanism used to cross the privilege boundary.
This distinction matters.
An attacker normally needs some way to execute code on the Windows machine before this type of vulnerability becomes useful.
For example, an attacker could potentially obtain that initial foothold through another vulnerability, malicious software, a compromised account, or a social-engineering attack.
PrettyPrague is then useful for moving from that lower-privileged execution context to a much more powerful one.
So it should not be described as a vulnerability that allows an attacker on the internet to directly take over any Windows PC running Avast.
However, that does not automatically prove that every Avast version, edition, configuration, and Windows release is affected.
Some technical analysis also identified configuration requirements around Avast's Sandbox functionality, meaning the real-world attack conditions can be narrower than a simple statement such as "every Avast user is vulnerable."
More importantly, Gen Digital has acknowledged the issue and stated that it has been fixed.
Therefore, the practical advice is simple:
Update Avast to the latest available version and keep automatic updates enabled.
Security software normally operates with very high privileges because it needs to inspect files, processes, drivers, and other parts of the operating system.
That makes security products an attractive target for privilege-escalation research.
If an attacker can find a mistake in the boundary between a normal process and a privileged security component, the vulnerability can potentially turn the security software's own privileges against the operating system.
That is exactly why vulnerabilities in antivirus products can be particularly dangerous.
The public PoC was reported to access the Windows SAM database and eventually spawn a SYSTEM shell through Avast's sandbox. The issue was serious because it could allow a lower-privileged local user to reach privileges that should have been unavailable to them.
The good news is that Gen Digital has acknowledged the vulnerability and stated that it has been fixed.
So if you are running Avast, the most important step is straightforward:
Keep Avast fully updated.
NT AUTHORITY\SYSTEM.The PoC was published by the researcher known as Nightmare Eclipse, also associated with the names Chaotic Eclipse, Infinite Nightmare, and MSNightmare. Independent security researchers reported that the exploit works against updated Windows 11 systems with Avast installed.
There is an important update, though: Gen Digital has since acknowledged the vulnerability and stated that the issue has been fixed. Users should therefore make sure Avast is fully updated rather than assuming that the public PoC means every current installation remains vulnerable.
What Is PrettyPrague?
PrettyPrague is a proof-of-concept exploit targeting the Avast Sandbox.The basic security problem is a local privilege escalation. An attacker who can already execute code as a lower-privileged user may be able to abuse Avast's privileged components to reach resources that should normally be protected from that user.
According to the research surrounding the PoC, the attack can:
- Access a copy of the Windows SAM database.
- Obtain local account credential information from the SAM.
- Abuse Avast's sandbox implementation.
- Eventually create a command shell running as
NT AUTHORITY\SYSTEM.
Why Is the Windows SAM File Important?
Windows uses the Security Account Manager (SAM) database to store information associated with local Windows accounts, including password-derived credential material.The live SAM database is normally protected from ordinary users. A standard process should not simply be able to open the file and read its contents.
An attacker who gains access to the SAM can potentially obtain valuable credential material for offline analysis and further attacks.
However, it is important to understand that the SAM does not simply contain your Windows password in plain text. Access to the database provides credential-related information, such as password hashes, rather than a readable list of everyone's actual passwords.
How Does Avast's Sandbox Fit Into the Attack?
A security sandbox is supposed to make potentially dangerous programs safer.Instead of allowing suspicious software to interact freely with the operating system, the security product places the process inside an isolated environment and restricts what it can access.
Avast's sandbox uses privileged components, including a kernel driver, to provide this isolation.
That creates an important security boundary:
A normal user should not be able to use the antivirus's privileged components to gain more privileges.
PrettyPrague reportedly found a way to abuse that boundary.
Research into the PoC indicates that Avast's sandbox virtualization could cause a protected SAM-related file to appear in a location accessible from outside the sandbox. The exploit then monitors the sandbox environment and attempts to obtain the redirected copy before it is removed.
In other words, the sandbox itself becomes part of the attack path rather than providing the expected protection.
How PrettyPrague Leads to SYSTEM
At a high level, the attack chain looks like this:- A lower-privileged process interacts with Avast's sandbox functionality.
- Avast runs the attacker's executable within the sandbox.
- The sandbox's virtualization mechanisms interact with protected Windows resources.
- A SAM-related copy becomes accessible through the sandbox environment.
- The attacker obtains sensitive credential information.
- The PoC continues the privilege-escalation chain and launches a shell as
NT AUTHORITY\SYSTEM.
The important security issue is the boundary between the unprivileged user, the Avast sandbox, and the privileged Avast components.
Why SYSTEM Access Is So Dangerous
Getting a SYSTEM shell is much more serious than simply gaining administrator privileges in a normal desktop scenario.A process running as
NT AUTHORITY\SYSTEM can interact with highly privileged Windows resources and services that are unavailable to ordinary users.Depending on the environment, an attacker with SYSTEM-level execution could potentially:
- Access protected system resources.
- Manipulate Windows services.
- Tamper with security software.
- Access sensitive local data.
- Steal or use credential material.
- Establish persistence.
- Deploy additional malicious software.
Ironically, the security product itself becomes the mechanism used to cross the privilege boundary.
Is This a Remote Attack?
No. PrettyPrague is primarily a local privilege-escalation issue.This distinction matters.
An attacker normally needs some way to execute code on the Windows machine before this type of vulnerability becomes useful.
For example, an attacker could potentially obtain that initial foothold through another vulnerability, malicious software, a compromised account, or a social-engineering attack.
PrettyPrague is then useful for moving from that lower-privileged execution context to a much more powerful one.
So it should not be described as a vulnerability that allows an attacker on the internet to directly take over any Windows PC running Avast.
Does the Vulnerability Affect Every Avast Installation?
The original researcher claimed broad Avast compatibility and reported testing the PoC on a fully patched Windows 11 25H2 system.However, that does not automatically prove that every Avast version, edition, configuration, and Windows release is affected.
Some technical analysis also identified configuration requirements around Avast's Sandbox functionality, meaning the real-world attack conditions can be narrower than a simple statement such as "every Avast user is vulnerable."
More importantly, Gen Digital has acknowledged the issue and stated that it has been fixed.
Therefore, the practical advice is simple:
Update Avast to the latest available version and keep automatic updates enabled.
What Should Avast Users Do?
If you use Avast on Windows, there is no reason to panic, but you should take the vulnerability seriously.- Update Avast to the latest available version.
- Make sure Windows is also fully updated.
- Restart the computer if Avast requests it.
- Avoid running unknown programs downloaded from untrusted sources.
- If you suspect that your computer was compromised while the vulnerable software was installed, investigate it rather than assuming an antivirus installation alone provides protection.
Why This Vulnerability Is Interesting
PrettyPrague is interesting for a reason beyond Avast itself.Security software normally operates with very high privileges because it needs to inspect files, processes, drivers, and other parts of the operating system.
That makes security products an attractive target for privilege-escalation research.
If an attacker can find a mistake in the boundary between a normal process and a privileged security component, the vulnerability can potentially turn the security software's own privileges against the operating system.
That is exactly why vulnerabilities in antivirus products can be particularly dangerous.
Final Takeaway
PrettyPrague demonstrates how a vulnerability in an antivirus sandbox can potentially turn a security mechanism into a privilege-escalation path.The public PoC was reported to access the Windows SAM database and eventually spawn a SYSTEM shell through Avast's sandbox. The issue was serious because it could allow a lower-privileged local user to reach privileges that should have been unavailable to them.
The good news is that Gen Digital has acknowledged the vulnerability and stated that it has been fixed.
So if you are running Avast, the most important step is straightforward:
Keep Avast fully updated.
Frequently Asked Questions
--------------------What is the PrettyPrague vulnerability?
PrettyPrague is a publicly released proof-of-concept targeting a privilege-escalation vulnerability in Avast's sandbox. The PoC reportedly accesses the Windows SAM database and can reach a SYSTEM-level shell.Does PrettyPrague reveal Windows passwords directly?
No. The SAM database does not store Windows passwords as plain text. It contains credential-related information, including password-derived hashes for local accounts.Does PrettyPrague allow remote hacking?
Not by itself. It is primarily a local privilege-escalation technique, meaning an attacker generally needs some ability to execute code on the target computer first.Has Avast fixed PrettyPrague?
Gen Digital has stated that it fixed the vulnerability and recommends keeping affected products up to date.Why is SYSTEM access dangerous?
NT AUTHORITY\SYSTEM is a highly privileged Windows security context. Code running with SYSTEM privileges can access and modify resources that are normally protected from standard users.