| CVE-2016-6581 | Date: (C)2017-01-11 (M)2023-12-22 |
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.
CVSS Score and Metrics +CVSS Score and Metrics -| CVSS V3 Severity: | CVSS V2 Severity: |
| CVSS Score : 7.5 | CVSS Score : 7.8 |
| Exploit Score: 3.9 | Exploit Score: 10.0 |
| Impact Score: 3.6 | Impact Score: 6.9 |
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| CVSS V3 Metrics: | CVSS V2 Metrics: |
| Attack Vector: NETWORK | Access Vector: NETWORK |
| Attack Complexity: LOW | Access Complexity: LOW |
| Privileges Required: NONE | Authentication: NONE |
| User Interaction: NONE | Confidentiality: NONE |
| Scope: UNCHANGED | Integrity: NONE |
| Confidentiality: NONE | Availability: COMPLETE |
| Integrity: NONE | |
| Availability: HIGH | |
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