VYPR
Get started
← All advisories
Moderate severityNVD Advisory· Published Feb 12, 2025· Updated Nov 3, 2025

Possible Log Injection in Rack::CommonLogger

CVE-2025-25184

Description

Rack provides an interface for developing web applications in Ruby. Prior to versions 2.2.11, 3.0.12, and 3.1.10, Rack::CommonLogger can be exploited by crafting input that includes newline characters to manipulate log entries. The supplied proof-of-concept demonstrates injecting malicious content into logs. When a user provides the authorization credentials via Rack::Auth::Basic, if success, the username will be put in env['REMOTE_USER'] and later be used by Rack::CommonLogger for logging purposes. The issue occurs when a server intentionally or unintentionally allows a user creation with the username contain CRLF and white space characters, or the server just want to log every login attempts. If an attacker enters a username with CRLF character, the logger will log the malicious username with CRLF characters into the logfile. Attackers can break log formats or insert fraudulent entries, potentially obscuring real activity or injecting malicious data into log files. Versions 2.2.11, 3.0.12, and 3.1.10 contain a fix.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
rackRubyGems
< 2.2.112.2.11
rackRubyGems
>= 3.0, < 3.0.123.0.12
rackRubyGems
>= 3.1, < 3.1.103.1.10

Affected products

1

Patches

1
074ae244430c

Escape non-printable characters when logging.

https://github.com/rack/rackJeremy EvansFeb 12, 2025via ghsa
commit
2 files changed · +9 −3
  • lib/rack/common_logger.rb+3 −2 modified
    @@ -20,7 +20,7 @@ class CommonLogger
     # The actual format is slightly different than the above due to the
     # separation of SCRIPT_NAME and PATH_INFO, and because the elapsed
     # time in seconds is included at the end.
-    FORMAT = %{%s - %s [%s] "%s %s%s%s %s" %d %s %0.4f\n}
+    FORMAT = %{%s - %s [%s] "%s %s%s%s %s" %d %s %0.4f }
 
     # +logger+ can be any object that supports the +write+ or +<<+ methods,
     # which includes the standard library Logger.  These methods are called
@@ -66,7 +66,8 @@ def log(env, status, response_headers, began_at)
         length,
         Utils.clock_time - began_at)
 
-      msg.gsub!(/[^[:print:]\n]/) { |c| sprintf("\\x%x", c.ord) }
+      msg.gsub!(/[^[:print:]]/) { |c| sprintf("\\x%x", c.ord) }
+      msg[-1] = "\n"
 
       logger = @logger || request.get_header(RACK_ERRORS)
       # Standard library logger doesn't support write but it supports << which actually
  • test/spec_common_logger.rb+6 −1 modified
    @@ -107,12 +107,17 @@ def with_mock_time(t = 0)
     (0..1).must_include duration.to_f
   end
 
-  it "escapes non printable characters except newline" do
+  it "escapes non printable characters including newline" do
     logdev = StringIO.new
     log = Logger.new(logdev)
     Rack::MockRequest.new(Rack::CommonLogger.new(app_without_lint, log)).request("GET\x1f", "/hello")
 
     logdev.string.must_match(/GET\\x1f \/hello HTTP\/1\.1/)
+
+    Rack::MockRequest.new(Rack::CommonLogger.new(app, log)).get("/", 'REMOTE_USER' => "foo\nbar", "QUERY_STRING" => "bar\nbaz")
+    logdev.string[-1].must_equal "\n"
+    logdev.string.must_include("foo\\xabar")
+    logdev.string.must_include("bar\\xabaz")
   end
 
   it "log path with PATH_INFO" do

Vulnerability mechanics

Generated by null/stub on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

6

News mentions

0

No linked articles in our index yet.