CVE-2016-6580
A HTTP/2 implementation built using any version of the Python priority library prior to version 1.2.0 could be targeted by a malicious peer by having that peer assign priority information for every possible HTTP/2 stream ID.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.81%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
A HTTP/2 implementation built using any version of the Python priority library prior to version 1.2.0 could be targeted by a malicious peer by having that peer assign priority information for every possible HTTP/2 stream ID. The priority tree would happily continue to store the priority information for each stream, and would therefore allocate unbounded amounts of memory. Attempting to actually use a tree like this would also cause extremely high CPU usage to maintain the tree.
- CVSS 3.0
- 7.5 HIGHCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 1.81% probability · 78th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-399
- Affected
- python/python priority library
- Source
- cve@mitre.org
EPSS 1.8% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- http://www.securityfocus.com/bid/92311Third Party Advisory, VDB Entry
- https://python-hyper.org/priority/en/latest/security/CVE-2016-6580.htmlMitigation, Vendor Advisory
- http://www.securityfocus.com/bid/92311Third Party Advisory, VDB Entry
- https://python-hyper.org/priority/en/latest/security/CVE-2016-6580.htmlMitigation, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.