CVE Catalog

CVE-2016-6581

High
Published: Translated: NVD NIST

Summary

A HTTP/2 implementation built using any version of the Python HPACK library between v1.0.0 and v2.2.0 could be targeted for a denial of service attack, specifically a so-called 'HPACK Bomb' attack. An attacker can insert a header field that is exactly the size of the HPACK dynamic header table, leading to a gigantic compression ratio.

Risk Assessment

The 'HPACK Bomb' attack can lead to server resource exhaustion, resulting in unavailability for users. Organizations may experience significant disruptions in service.

Recommendation

It is recommended to update the Python HPACK library to a version newer than v2.2.0 to minimize the risk of attack. Additionally, monitoring network traffic for suspicious activities is advisable.

Related vulnerabilities

Original NVD description (English source)

A HTTP/2 implementation built using any version of the Python HPACK library between v1.0.0 and v2.2.0 could be targeted for a denial of service attack, specifically a so-called "HPACK Bomb" attack. This attack occurs when an attacker inserts a header field that is exactly the size of the HPACK dynamic header table into the dynamic header table. The attacker can then send a header block that is simply repeated requests to expand that field in the dynamic table. This can lead to a gigantic compression ratio of 4,096 or better, meaning that 16kB of data can decompress to 64MB of data on the target machine.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS