CVE-2021-41136

Advisory lineage Upstream: 0 Downstream: 12
Modified
Published: 12 Oct 2021, 15:30
Last modified:27 May 2025, 15:16

Vulnerability Summary

Overall Risk (default)
low
15/100
CVSS Score
3.7 LOW
v3.1 (cve.org)
EPSS Score
0.29% LOW
0% probability 0.00%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

12 Oct 2021, 15:30
Published
Vulnerability first disclosed
27 May 2025, 15:16
Last Modified
Vulnerability information updated

Description

Puma is a HTTP 1.1 server for Ruby/Rack applications. Prior to versions 5.5.1 and 4.3.9, using `puma` with a proxy which forwards HTTP header values which contain the LF character could allow HTTP request smugggling. A client could smuggle a request through a proxy, causing the proxy to send a response back to another unknown client. The only proxy which has this behavior, as far as the Puma team is aware of, is Apache Traffic Server. If the proxy uses persistent connections and the client adds another request in via HTTP pipelining, the proxy may mistake it as the first request's body. Puma, however, would see it as two requests, and when processing the second request, send back a response that the proxy does not expect. If the proxy has reused the persistent connection to Puma to send another request for a different client, the second response from the first client will be sent to the second client. This vulnerability was patched in Puma 5.5.1 and 4.3.9. As a workaround, do not use Apache Traffic Server with `puma`.

CVSS Metrics

  • v3.1•LOW•Score: 3.7CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N
  • v2.0•LOW•Score: 3.6AV:N/AC:H/Au:S/C:P/I:P/A:N

EPSS Trends

Current EPSS score: 0.29%• Percentile: 52%

Techniques & Countermeasures

  • CWE-444•Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

    The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.

Affected Systems

  • debian•debian_linux

    10.0 | 11.0

  • puma•puma

    ≤ 4.3.8 | ≥ 5.0.0, ≤ 5.5.0 | ≥ 5.0.0, < 5.5.1 | < 4.3.9

References (7)