Puma is a concurrent HTTP 1.1 server for Ruby/Rack applications. 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 and a git patch is available for those using unsupported versions of Puma.
Published 2021-05-11 17:15:08
Updated 2022-10-27 12:39:51
Source GitHub, Inc.
View at NVD,   CVE.org

Exploit prediction scoring system (EPSS) score for CVE-2021-29509

Probability of exploitation activity in the next 30 days: 1.02%

Percentile, the proportion of vulnerabilities that are scored at or less: ~ 83 % EPSS Score History EPSS FAQ

CVSS scores for CVE-2021-29509

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source
5.0
MEDIUM AV:N/AC:L/Au:N/C:N/I:N/A:P
10.0
2.9
NIST
7.5
HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.9
3.6
NIST
7.5
HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.9
3.6
GitHub, Inc.

CWE ids for CVE-2021-29509

  • The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
    Assigned by: security-advisories@github.com (Primary)
  • The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.
    Assigned by: nvd@nist.gov (Secondary)

References for CVE-2021-29509

Products affected by CVE-2021-29509

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