CVE-2016-6581: n/a vulnerability

CVE-2016-6581: A HTTP/2 implementation built using any version of the Python HPACK library between v1.0.0 and v2.2.0 could...

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.

UnknownCVSS not scoredNot KEV-listedUpdatedAug 6, 2024, 01:36 UTC (UTC+00:00)

Security readout for executives and security teams

CVE-2016-6581 is a denial-of-service risk in Python HPACK versions 1.0.0 through 2.2.0. A small compressed HTTP/2 header block may expand dramatically in memory, potentially exhausting resources in affected services. Exposure is most likely in Python-based HTTP/2 servers, proxies, or libraries that embed Python HPACK v1.0.0 through v2.2.0. The source bundle does not enumerate affected products. Treat this as a targeted availability risk, not confirmed compromise. Prioritize internet-facing HTTP/2 services and products with Python HPACK dependency evidence. Mitigation focus: Inventory services and dependencies using Python HPACK.; Remove or replace HPACK versions 1.0.0 through 2.2.0.; Check python-hyper HPACK guidance for fixed-version direction..

Prepared: Jun 13, 2026, 12:51 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2016-6581 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup

Vulnerability profileCVE Program record

Severity: Unknown
CVSS: Not scored
Known Exploited: No
Published: Jan 10, 2017, 15:00 UTC (UTC+00:00)

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors

0Timeline events

0ADP providers

2Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

CVE List V5 sourceCVE List V5
https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.htmlCVE reference · x_refsource_CONFIRM

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus

n/an/an/aListed

Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.