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Vulnerability details: VCID-62kh-vbh8-7fb8
Vulnerability ID VCID-62kh-vbh8-7fb8
Aliases CVE-2021-41136
GHSA-48w2-rm65-62xx
Summary 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: * Nginx * Apache (>2.4.25) * Haproxy * Caddy * Traefik ### Possible Breakage If you are [dealing with legacy clients that want to send `LF` as a line ending](https://stackoverflow.com/questions/43574428/have-apache-accept-lf-vs-crlf-in-request-headers) in an HTTP header, this will cause those clients to receive a `400` error. ### References * [HTTP Request Smuggling](https://portswigger.net/web-security/request-smuggling) ### For more information If you have any questions or comments about this advisory: * Open an issue in [Puma](https://github.com/puma/puma) * See our [security policy](https://github.com/puma/puma/security/policy)
Status Published
Exploitability None
Weighted Severity None
Risk None
Affected and Fixed Packages Package Details
Weaknesses (3)
CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
cvssv3 3.7 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-41136.json
epss 0.00288 https://api.first.org/data/v1/epss?cve=CVE-2021-41136
cvssv3.1 3.7 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv3.1 3.7 https://github.com/puma/puma
generic_textual LOW https://github.com/puma/puma
cvssv3.1 3.7 https://github.com/puma/puma/commit/436c71807f00e07070902a03f79fd3e130eb6b18
generic_textual LOW https://github.com/puma/puma/commit/436c71807f00e07070902a03f79fd3e130eb6b18
cvssv3.1 3.7 https://github.com/puma/puma/commit/acdc3ae571dfae0e045cf09a295280127db65c7f
generic_textual LOW https://github.com/puma/puma/commit/acdc3ae571dfae0e045cf09a295280127db65c7f
cvssv3.1 3.7 https://github.com/puma/puma/commit/fb6ad8f8013ab5cdbb2f444cbfabd0b4fde71139
generic_textual LOW https://github.com/puma/puma/commit/fb6ad8f8013ab5cdbb2f444cbfabd0b4fde71139
cvssv3.1 3.7 https://github.com/puma/puma/releases/tag/v4.3.9
generic_textual LOW https://github.com/puma/puma/releases/tag/v4.3.9
cvssv3.1 3.7 https://github.com/puma/puma/releases/tag/v5.5.1
generic_textual LOW https://github.com/puma/puma/releases/tag/v5.5.1
cvssv3 3.7 https://github.com/puma/puma/security/advisories/GHSA-48w2-rm65-62xx
cvssv3.1 3.7 https://github.com/puma/puma/security/advisories/GHSA-48w2-rm65-62xx
generic_textual LOW https://github.com/puma/puma/security/advisories/GHSA-48w2-rm65-62xx
cvssv3.1 3.7 https://github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2021-41136.yml
generic_textual LOW https://github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2021-41136.yml
cvssv3.1 3.7 https://lists.debian.org/debian-lts-announce/2022/08/msg00015.html
generic_textual LOW https://lists.debian.org/debian-lts-announce/2022/08/msg00015.html
cvssv3.1 3.7 https://nvd.nist.gov/vuln/detail/CVE-2021-41136
generic_textual LOW https://nvd.nist.gov/vuln/detail/CVE-2021-41136
archlinux High https://security.archlinux.org/AVG-2764
cvssv3.1 3.7 https://security.gentoo.org/glsa/202208-28
generic_textual LOW https://security.gentoo.org/glsa/202208-28
cvssv3.1 3.7 https://www.debian.org/security/2022/dsa-5146
generic_textual LOW https://www.debian.org/security/2022/dsa-5146
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-41136.json
https://api.first.org/data/v1/epss?cve=CVE-2021-41136
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-41136
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-23634
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-24790
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://github.com/puma/puma
https://github.com/puma/puma/commit/436c71807f00e07070902a03f79fd3e130eb6b18
https://github.com/puma/puma/commit/acdc3ae571dfae0e045cf09a295280127db65c7f
https://github.com/puma/puma/commit/fb6ad8f8013ab5cdbb2f444cbfabd0b4fde71139
https://github.com/puma/puma/releases/tag/v4.3.9
https://github.com/puma/puma/releases/tag/v5.5.1
https://github.com/puma/puma/security/advisories/GHSA-48w2-rm65-62xx
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2021-41136.yml
https://lists.debian.org/debian-lts-announce/2022/08/msg00015.html
https://nvd.nist.gov/vuln/detail/CVE-2021-41136
https://security.gentoo.org/glsa/202208-28
https://www.debian.org/security/2022/dsa-5146
2013495 https://bugzilla.redhat.com/show_bug.cgi?id=2013495
AVG-2764 https://security.archlinux.org/AVG-2764
GHSA-48w2-rm65-62xx https://github.com/advisories/GHSA-48w2-rm65-62xx
RHSA-2022:5498 https://access.redhat.com/errata/RHSA-2022:5498
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-41136.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://github.com/puma/puma
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://github.com/puma/puma/commit/436c71807f00e07070902a03f79fd3e130eb6b18
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://github.com/puma/puma/commit/acdc3ae571dfae0e045cf09a295280127db65c7f
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://github.com/puma/puma/commit/fb6ad8f8013ab5cdbb2f444cbfabd0b4fde71139
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://github.com/puma/puma/releases/tag/v4.3.9
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://github.com/puma/puma/releases/tag/v5.5.1
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://github.com/puma/puma/security/advisories/GHSA-48w2-rm65-62xx
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2021-41136.yml
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://lists.debian.org/debian-lts-announce/2022/08/msg00015.html
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-41136
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://security.gentoo.org/glsa/202208-28
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Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N Found at https://www.debian.org/security/2022/dsa-5146
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

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Exploit Prediction Scoring System (EPSS)
Percentile 0.52426
EPSS Score 0.00288
Published At May 29, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-05-29T09:12:05.187971+00:00 GithubOSV Importer Import https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/10/GHSA-48w2-rm65-62xx/GHSA-48w2-rm65-62xx.json 38.6.0