7.5 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5 Medium
CVSS2
Access Vector
NETWORK
Access Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:N/I:N/A:P
0.01 Low
EPSS
Percentile
83.6%
This vulnerability is related to CVE-2019-16770.
The fix for CVE-2019-16770 was incomplete. The original fix only protected existing connections that had already been accepted from having their requests starved by greedy persistent-connections saturating all threads in the same process. However, new connections may still be starved by greedy persistent-connections saturating all threads in all processes in the cluster.
A puma
server which received more concurrent keep-alive
connections than the server had threads in its threadpool would service only a subset of connections, denying service to the unserved connections.
This problem has been fixed in puma
4.3.8 and 5.3.1.
Setting queue_requests false
also fixes the issue. This is not advised when using puma
without a reverse proxy, such as nginx
or apache
, because you will open yourself to slow client attacks (e.g. slowloris).
The fix is very small. A git patch is available here for those using unsupported versions of Puma.
If you have any questions or comments about this advisory:
Thank you to @MSP-Greg, @wjordan and @evanphx for their review on this issue.
Thank you to @ioquatix for providing a modified fork of wrk
which made debugging this issue much easier.
gist.github.com/nateberkopec/4b3ea5676c0d70cbb37c82d54be25837
github.com/advisories/GHSA-q28m-8xjw-8vr5
github.com/puma/puma/security/advisories/GHSA-q28m-8xjw-8vr5
github.com/puma/puma/security/policy
github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2021-29509.yml
lists.debian.org/debian-lts-announce/2022/08/msg00015.html
nvd.nist.gov/vuln/detail/CVE-2021-29509
rubygems.org/gems/puma
security.gentoo.org/glsa/202208-28
7.5 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5 Medium
CVSS2
Access Vector
NETWORK
Access Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:N/I:N/A:P
0.01 Low
EPSS
Percentile
83.6%