CVE catalog
CVE-2016-6581
python-hpack: CVE-2016-6581
- Severity
- High · CVSS 7.5
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 1.83% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | python-hpack | sid | 4.0.0-4 | fixed |
| Debian | python-hpack | forky | 4.0.0-4 | fixed |
| Debian | python-hpack | trixie | 4.0.0-3 | fixed |
| Debian | python-hpack | bookworm | 4.0.0-2 | fixed |
| Opensuse | python-hpack | tumbleweed | 4.2.0-1.1 | fixed |
| Opensuse | python-hpack | tumbleweed | 4.0.0-2.7 | fixed |
| Ubuntu | python-hpack | 16.04 | 1.1.0-1 | vulnerable |
| Ubuntu | python-hpack | 16.04 | 2.0.1-1 | vulnerable |
| Ubuntu | python-hpack | 16.04 | 2.1.0-1 | vulnerable |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | python-hpack | source | sid | 2.3.0-1 | not yet assigned | Not reported | [833467] |
| Debian | python-hpack | source | forky | 2.3.0-1 | not yet assigned | Not reported | [833467] |
| Debian | python-hpack | source | trixie | 2.3.0-1 | not yet assigned | Not reported | [833467] |
| Debian | python-hpack | source | bookworm | 2.3.0-1 | not yet assigned | Not reported | [833467] |
| Opensuse | python-hpack | rpm | tumbleweed | 4.2.0-1.1 | Not reported | OPENSUSE-SU-2026:11556-1 | Not reported |
| Opensuse | python-hpack | rpm | tumbleweed | 4.0.0-2.7 | Not reported | OPENSUSE-SU-2024:14140-1 | Not reported |
OpenFactory catalog packages
[openSUSE Tumbleweed]
- [python313-hpack]Unknown
Source package: [python-hpack]
Details (1)
4.2.0-1.1· noarch · tumbleweedUnknown · Fixed:
4.0.0-2.7, 4.2.0-1.1Version impact unknown
dsa · python-hpack · opensuse · tumbleweed
- [python314-hpack]Unknown
Source package: [python-hpack]
Details (1)
4.2.0-1.1· noarch · tumbleweedUnknown · Fixed:
4.0.0-2.7, 4.2.0-1.1Version impact unknown
dsa · python-hpack · opensuse · tumbleweed
[Debian 12 (Bookworm)]
- [python3-hpack]Fixed
Source package: [python-hpack]
Details (2)
4.0.0-2· all · bookwormFixed · Fixed:
2.3.0-1dsa · python-hpack · debian · bookworm; dsa · python-hpack · debian · 12
4.0.0-2· all · bookwormFixed · Fixed:
2.3.0-1dsa · python-hpack · debian · bookworm; dsa · python-hpack · debian · 12
[Debian 13 (Trixie)]
- [python3-hpack]Fixed
Source package: [python-hpack]
Details (2)
4.0.0-3· all · trixieFixed · Fixed:
2.3.0-1dsa · python-hpack · debian · 13
4.0.0-3· all · trixieFixed · Fixed:
2.3.0-1dsa · python-hpack · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/opensuse-su-2026_11556-1.json]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2016-6581]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2016-6581]
- [https://osv.dev/vulnerability/openSUSE-SU-2024:14140-1]
- [https://osv.dev/vulnerability/openSUSE-SU-2026:11556-1]
- [https://security-tracker.debian.org/tracker/CVE-2016-6581]
[Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database] · [SUSE security advisories and VEX]