Puma is a simple, fast, multi-threaded, and highly parallel HTTP 1.1 server
for Ruby/Rack applications. Puma is intended for use in both development and
production environments. It's great for highly parallel Ruby implementations such as
JRuby and TruffleRuby as well as as providing process worker support to support CRuby well.
Clients could clobber values set by intermediate proxies (such as X-Forwarded-For) by providing a underscore version of the same header (X-Forwarded_For). Any users trusting headers set by their proxy may be affected. Attackers may be able to downgrade connections to HTTP (non-SSL) or redirect responses, which could cause confidentiality leaks if combined with a separate MITM attack.
Patches
v6.4.3/v5.6.9 now discards any headers using underscores if the non-underscore version also exists. Effectively, allowing the proxy defined headers to always win.
Workarounds
Nginx has a underscoresinheaders configuration variable to discard these headers at the proxy level.
Any users that are implicitly trusting the proxy defined headers for security or availability should immediately cease doing so until upgraded to the fixed versions.
Prior to versions 6.4.2 and 5.6.8, puma exhibited dangerous behavior when parsing chunked transfer encoding bodies.
Fixed versions limit the size of chunk extensions. Without this limit, an attacker could cause unbounded resource (CPU, network bandwidth) consumption.
Patches
The vulnerability has been fixed in 6.4.2 and 5.6.8.
Prior to version 6.3.1, puma exhibited incorrect behavior when parsing chunked transfer encoding bodies and zero-length Content-Length headers in a way that allowed HTTP request smuggling.
The following vulnerabilities are addressed by this advisory:
- Incorrect parsing of trailing fields in chunked transfer encoding bodies
- Parsing of blank/zero-length Content-Length headers\r\n
Patches
The vulnerability has been fixed in 6.3.1 and 5.6.7.
Prior to versions 6.4.2 and 5.6.8, puma exhibited incorrect
behavior when parsing chunked transfer encoding bodies in a
way that allowed HTTP request smuggling.
Fixed versions limit the size of chunk extensions. Without this
limit, an attacker could cause unbounded resource (CPU, network
bandwidth) consumption.
Patches
The vulnerability has been fixed in 6.4.2 and 5.6.8.
Clients could clobber values set by intermediate proxies (such as
X-Forwarded-For) by providing a underscore version of the same
header (X-Forwarded_For).
Any users trusting headers set by their proxy may be affected.
Attackers may be able to downgrade connections to HTTP (non-SSL)
or redirect responses, which could cause confidentiality leaks
if combined with a separate MITM attack.
Patches
v6.4.3/v5.6.9 now discards any headers using underscores if the
non-underscore version also exists. Effectively, allowing the
proxy defined headers to always win.
Workarounds
Nginx has a underscoresinheaders
configuration variable to discard these headers at the proxy level.
Any users that are implicitly trusting the proxy defined headers
for security or availability should immediately cease doing so
until upgraded to the fixed versions.
Prior to version 6.3.1, puma exhibited incorrect behavior when parsing chunked transfer encoding bodies and zero-length Content-Length headers in a way that allowed HTTP request smuggling.
The following vulnerabilities are addressed by this advisory:
- Incorrect parsing of trailing fields in chunked transfer encoding bodies
- Parsing of blank/zero-length Content-Length headers\r\n
Patches
The vulnerability has been fixed in 6.3.1 and 5.6.7.
