CVE-2020-36846 is a critical security vulnerability identified in the TIMLEGGE IO::Compress::Brotli Perl module, specifically affecting versions prior to 0.007. The root cause is a buffer overflow in the embedded Brotli compression library, which is a widely used compression algorithm. This vulnerability stems from the use of an outdated Brotli library version prior to 1.0.8, which improperly handles "one-shot" decompression requests when the input length is controlled by an attacker. The flaw manifests when the decompression process attempts to copy chunks of data larger than 2 GiB, leading to a buffer overflow and subsequent crash or potential arbitrary code execution. The vulnerability is classified under CWE-1395, indicating dependency on a vulnerable third-party component. Exploitation requires no privileges or user interaction, and the attack vector is network-based, making it remotely exploitable. The CVSS v3.1 score of 9.8 reflects the high impact on confidentiality, integrity, and availability, as successful exploitation could allow attackers to execute arbitrary code, cause denial of service, or compromise system integrity. The recommended remediation is to upgrade the IO::Compress::Brotli module to version 0.007 or later, which includes the updated Brotli library version 1.0.8 or above. If upgrading is not feasible, it is advised to avoid the "one-shot" decompression API and instead use the "streaming" API with strict chunk size limits to mitigate the risk of buffer overflow. No known exploits are currently reported in the wild, but the severity and ease of exploitation warrant immediate attention.

For European organizations, this vulnerability poses a significant risk, especially for those relying on Perl-based applications or services that utilize the IO::Compress::Brotli module for data compression and decompression. Exploitation could lead to system crashes, denial of service, or potentially remote code execution, compromising sensitive data confidentiality and system integrity. Industries such as finance, healthcare, telecommunications, and government agencies, which often handle large volumes of compressed data, could be particularly affected. The remote and unauthenticated nature of the exploit increases the attack surface, potentially allowing attackers to target exposed services or web applications that decompress Brotli-compressed data. This could disrupt critical services, lead to data breaches, or facilitate lateral movement within networks. Additionally, the dependency on a vulnerable third-party component highlights supply chain risks, where indirect usage of the affected module in larger software stacks could propagate the vulnerability. Given the high CVSS score and critical severity, European organizations must prioritize patching and mitigation to prevent exploitation and maintain compliance with data protection regulations such as GDPR.

1. Immediate upgrade of the IO::Compress::Brotli Perl module to version 0.007 or later, ensuring the embedded Brotli library is updated to version 1.0.8 or above. 2. If upgrading is not immediately possible, refactor applications to avoid using the "one-shot" decompression API; instead, implement the "streaming" API with enforced chunk size limits to prevent processing excessively large data chunks. 3. Conduct a thorough inventory of all software components and dependencies to identify indirect usage of the vulnerable module, including third-party applications and libraries. 4. Implement network-level protections such as web application firewalls (WAFs) to detect and block anomalous decompression requests with unusually large input lengths. 5. Monitor application logs and system behavior for signs of crashes or abnormal decompression activity that could indicate attempted exploitation. 6. Engage in secure software development lifecycle (SDLC) practices to regularly update and audit third-party dependencies, reducing future supply chain risks. 7. Educate development and operations teams about the risks of using outdated compression libraries and the importance of timely patching.