CVE-2020-36846: Buffer Overflow in Brotli Library Affecting Bitnami PowerShell
Summary
CVE-2020-36846: Buffer overflow in Brotli library. Affects powershell across 3 version ranges.
>= 7.0.0, < 7.0.9
>= 7.1.0, < 7.1.6
>= 7.2.0, < 7.2.2
Fixed in 7.0.9, 7.1.6 or 7.2.2, depending on the release line you run. How to fix ↓
Also tracked for
- github.com/google/brotli · Go
- dotnet-sdk · Bitnami
- dotnet · Bitnami
- brotli · Bitnami
- brotli-sys · crates.io
- compu-brotli-sys · crates.io
- brotli · Alpine:v3.12
- brotli · PyPI
The same CVE-2020-36846 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
PowerShell is a task automation and configuration management framework from Microsoft, consisting of a command-line shell and associated scripting language. It is widely used for managing system configurations and automating administrative tasks. The vulnerability in question arises from the Brotli library, which is utilized for data compression and decompression in various applications, including PowerShell. This vulnerability can lead to severe consequences if exploited, as it allows for a buffer overflow that can crash the application.
Vulnerability Detail
A buffer overflow exists in the Brotli library versions prior to 1.0.8. This vulnerability can be exploited by an attacker who controls the input length of a 'one-shot' decompression request to a script. The overflow occurs when copying over chunks of data larger than 2 GiB, potentially leading to application crashes and denial of service. The affected versions of PowerShell are 7.0.0 to 7.0.8, 7.1.0 to 7.1.5, and 7.2.0 to 7.2.1.
How To Fix
Fixed versions by release line
The minimum fixed version depends on the release line you run.
-
>= 7.0.0, < 7.0.97.0.9 -
>= 7.1.0, < 7.1.67.1.6 -
>= 7.2.0, < 7.2.27.2.2
Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →
Workaround
If you cannot update the Brotli library, consider using the 'streaming' API instead of the 'one-shot' API, and impose chunk size limits to mitigate the risk of buffer overflow.
Conclusion
The buffer overflow vulnerability in the Brotli library poses a significant risk to applications using affected versions of PowerShell. It is crucial to update to the patched versions or implement workarounds to mitigate potential exploitation. Regular monitoring for vulnerabilities using tools like Vulert can help maintain application security.
See every vulnerability recorded for powershell →
FAQ
CVE-2020-36846 is a vulnerability in the Brotli library that can lead to a buffer overflow in applications using affected versions, including Bitnami PowerShell.
You can check if your application is affected by using the Vulert playground at Vulert Scanner, which analyzes your manifest file for vulnerabilities.
Exploiting this vulnerability can lead to application crashes and denial of service, potentially allowing attackers to disrupt services.
Yes, you can use the 'streaming' API instead of the 'one-shot' API and impose chunk size limits to reduce the risk of buffer overflow.
More information can be found in the vulnerability details on GitHub or by visiting the official Bitnami documentation.
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