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Security Advisories: GSA_kwCzR0hTQS00OHcyLXJtNjUtNjJ4eM0Whw

Puma with proxy which forwards LF characters as line endings could allow HTTP request smuggling

Impact

Prior to puma version 5.5.0, using puma with a proxy which forwards LF characters as line endings could allow HTTP request smuggling. A client could smuggle a request through a proxy, causing the proxy to send a response back to another unknown client.

This behavior (forwarding LF characters as line endings) is very uncommon amongst proxy servers, so we have graded the impact here as "low". Puma is only aware of a single proxy server which has this behavior.

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.

Patches

This vulnerability was patched in Puma 5.5.1 and 4.3.9.

Workarounds

This vulnerability only affects Puma installations without any proxy in front.

Use a proxy which does not forward LF characters as line endings.

Proxies which do not forward LF characters as line endings:

Possible Breakage

If you are dealing with legacy clients that want to send LF as a line ending in an HTTP header, this will cause those clients to receive a 400 error.

References

For more information

If you have any questions or comments about this advisory:

Permalink: https://github.com/advisories/GHSA-48w2-rm65-62xx
JSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS00OHcyLXJtNjUtNjJ4eM0Whw
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Low
Classification: General
Published: over 2 years ago
Updated: 12 months ago


CVSS Score: 3.7
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N

Identifiers: GHSA-48w2-rm65-62xx, CVE-2021-41136
References: Repository: https://github.com/puma/puma
Blast Radius: 20.7

Affected Packages

rubygems:puma
Dependent packages: 627
Dependent repositories: 404,320
Downloads: 357,648,490 total
Affected Version Ranges: < 4.3.9, >= 5.0.0, < 5.5.1
Fixed in: 4.3.9, 5.5.1
All affected versions: 0.8.0, 0.8.1, 0.8.2, 0.9.0, 0.9.1, 0.9.2, 0.9.3, 0.9.4, 0.9.5, 1.0.0, 1.1.0, 1.1.1, 1.2.0, 1.2.1, 1.2.2, 1.3.0, 1.3.1, 1.4.0, 1.5.0, 1.6.0, 1.6.1, 1.6.2, 1.6.3, 2.0.0, 2.0.1, 2.1.0, 2.1.1, 2.2.0, 2.2.1, 2.2.2, 2.3.0, 2.3.1, 2.3.2, 2.4.0, 2.4.1, 2.5.0, 2.5.1, 2.6.0, 2.7.0, 2.7.1, 2.8.0, 2.8.1, 2.8.2, 2.9.0, 2.9.1, 2.9.2, 2.10.0, 2.10.1, 2.10.2, 2.11.0, 2.11.1, 2.11.2, 2.11.3, 2.12.0, 2.12.1, 2.12.2, 2.12.3, 2.13.0, 2.13.1, 2.13.2, 2.13.3, 2.13.4, 2.14.0, 2.15.0, 2.15.1, 2.15.2, 2.15.3, 2.16.0, 3.0.0, 3.0.1, 3.0.2, 3.1.0, 3.1.1, 3.2.0, 3.3.0, 3.4.0, 3.5.0, 3.5.1, 3.5.2, 3.6.0, 3.6.1, 3.6.2, 3.7.0, 3.7.1, 3.8.0, 3.8.1, 3.8.2, 3.9.0, 3.9.1, 3.10.0, 3.11.0, 3.11.1, 3.11.2, 3.11.3, 3.11.4, 3.12.0, 3.12.1, 3.12.2, 3.12.4, 3.12.5, 3.12.6, 4.0.0, 4.0.1, 4.1.0, 4.1.1, 4.2.0, 4.2.1, 4.3.0, 4.3.1, 4.3.3, 4.3.4, 4.3.5, 4.3.6, 4.3.7, 4.3.8, 5.0.0, 5.0.1, 5.0.2, 5.0.3, 5.0.4, 5.1.0, 5.1.1, 5.2.0, 5.2.1, 5.2.2, 5.3.0, 5.3.1, 5.3.2, 5.4.0, 5.5.0
All unaffected versions: 4.3.9, 4.3.10, 4.3.11, 4.3.12, 5.5.1, 5.5.2, 5.6.0, 5.6.1, 5.6.2, 5.6.4, 5.6.5, 5.6.6, 5.6.7, 5.6.8, 6.0.0, 6.0.1, 6.0.2, 6.1.0, 6.1.1, 6.2.0, 6.2.1, 6.2.2, 6.3.0, 6.3.1, 6.4.0, 6.4.1, 6.4.2