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.
Advisories
Source ID Title
EUVD EUVD EUVD-2017-0059 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.
Github GHSA Github GHSA GHSA-ffq8-576r-v26g HPACK Denial of Service vulnerability (HPACK Bomb)
Fixes

Solution

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Workaround

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cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published:

Updated: 2024-08-06T01:36:28.459Z

Reserved: 2016-08-03T00:00:00

Link: CVE-2016-6581

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Deferred

Published: 2017-01-10T15:59:00.423

Modified: 2025-04-20T01:37:25.860

Link: CVE-2016-6581

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

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Weaknesses