PYSEC-2017-87

Vulnerability from pysec - Published: 2017-01-10 15:59 - Updated: 2021-08-27 03:22
VLAI
Details

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.

Impacted products
Name purl
hpack pkg:pypi/hpack
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "hpack",
        "purl": "pkg:pypi/hpack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.0.0",
        "1.0.1",
        "1.1.0",
        "2.0.0",
        "2.0.1",
        "2.1.0",
        "2.1.1",
        "2.2.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2016-6581",
    "GHSA-ffq8-576r-v26g"
  ],
  "details": "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.",
  "id": "PYSEC-2017-87",
  "modified": "2021-08-27T03:22:04.412157Z",
  "published": "2017-01-10T15:59:00Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html"
    },
    {
      "type": "WEB",
      "url": "http://www.securityfocus.com/bid/92315"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-ffq8-576r-v26g"
    }
  ]
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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