CVE-2020-36846 in IO::Compress::Brotli
Summary
by MITRE • 05/30/2025
A buffer overflow, as described in CVE-2020-8927, exists in the embedded Brotli library. Versions of IO::Compress::Brotli prior to 0.007 included a version of the brotli library prior to version 1.0.8, where an attacker controlling the input length of a "one-shot" decompression request to a script can trigger a crash, which happens when copying over chunks of data larger than 2 GiB. It is recommended to update your IO::Compress::Brotli module to 0.007 or later. If one cannot update, we recommend to use the "streaming" API as opposed to the "one-shot" API, and impose chunk size limits.
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Analysis
by VulDB Data Team • 05/31/2025
The vulnerability identified as CVE-2020-36846 represents a critical buffer overflow condition within the embedded Brotli compression library used by the Perl module IO::Compress::Brotli. This flaw stems from a specific implementation issue where the decompression process fails to properly validate input parameters during one-shot decompression operations, creating a pathway for arbitrary code execution or system instability. The vulnerability specifically affects versions prior to 0.007 of the IO::Compress::Brotli module, which incorporated a Brotli library version earlier than 1.0.8, making it susceptible to memory corruption during data processing.
The technical exploitation of this vulnerability occurs when an attacker manipulates the input length parameter in a one-shot decompression request, causing the decompression routine to attempt copying data chunks exceeding the 2 gigabyte threshold. This scenario triggers a classic buffer overflow condition where the system attempts to write beyond allocated memory boundaries, resulting in application crashes or potential memory corruption that could be leveraged for more severe attacks. The flaw operates at the memory management level, where insufficient bounds checking allows for excessive memory allocation and data copying operations that exceed system limits.
The operational impact of this vulnerability extends beyond simple application crashes to potentially enable remote code execution in scenarios where the affected Perl applications process untrusted input data. Systems utilizing IO::Compress::Brotli for decompressing user-supplied or network-received compressed data become vulnerable to denial of service attacks or more sophisticated exploitation attempts. The vulnerability is particularly concerning in web applications or services that accept compressed data inputs, as it creates a vector for attackers to destabilize services through carefully crafted malicious input sequences that trigger the buffer overflow condition.
Security practitioners should note this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and maps to ATT&CK technique T1059.007 for command and scripting interpreter execution. The recommended mitigation strategy involves immediate upgrading to IO::Compress::Brotli version 0.007 or later, which incorporates the patched Brotli library version 1.0.8 or higher. When immediate updates are not feasible, administrators should implement defensive programming practices by switching from the one-shot API to the streaming API, which provides better memory management and input validation. Additionally, implementing chunk size limitations in input processing routines serves as an effective compensating control that prevents the overflow condition from being triggered through excessive input parameters.