CVE-2024-22049

httparty before 0.21.0 is vulnerable to an assumed-immutable web parameter vulnerability. A remote and unauthenticated attacker can provide a crafted filename parameter during multipart/form-data uploads which could result in attacker controlled filenames being written.

httparty before 0.21.0 is vulnerable to an assumed-immutable web parameter vulnerability. A remote and unauthenticated attacker can provide a crafted filename parameter during multipart/form-data uploads which could result in attacker controlled filenames being written.

httparty before 0.21.0 is vulnerable to an assumed-immutable web parameter vulnerability. A remote and unauthenticated attacker can provide a crafted filename parameter during multipart/form-data uploads which could result in attacker controlled filenames being written.

Impact

I found "multipart/form-data request tampering vulnerability" caused by Content-Disposition "filename" lack of escaping in httparty.

httparty/lib/httparty/request > body.rb > def generate_multipart

https://github.com/jnunemaker/httparty/blob/4416141d37fd71bdba4f37589ec265f55aa446ce/lib/httparty/request/body.rb#L43

By exploiting this problem, the following attacks are possible

• An attack that rewrites the "name" field according to the crafted file name, impersonating (overwriting) another field.
• Attacks that rewrite the filename extension at the time multipart/form-data is generated by tampering with the filename

For example, this vulnerability can be exploited to generate the following Content-Disposition.

Normal Request example: normal input filename: abc.txt

generated normal header in multipart/form-data Content-Disposition: form-data; name="avatar"; filename="abc.txt"

Malicious Request example malicious input filename: overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt

generated malicious header in multipart/form-data: Content-Disposition: form-data; name="avatar"; filename="overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt"

The Abused Header has multiple name ( avatar & foo ) fields and the "filename" has been rewritten from *.txt to *.sh .

These problems can result in successful or unsuccessful attacks, depending on the behavior of the parser receiving the request. I have confirmed that the attack succeeds, at least in the following frameworks

• Spring (Java)
• Ktor (Kotlin)
• Ruby on Rails (Ruby)

The cause of this problem is the lack of escaping of the " (Double-Quote) character in Content-Disposition > filename.

WhatWG's HTML spec has an escaping requirement.

https://html.spec.whatwg.org/#multipart-form-data

For field names and filenames for file fields, the result of the encoding in the previous bullet point must be escaped by replacing any 0x0A (LF) bytes with the byte sequence %0A, 0x0D (CR) with %0D and 0x22 (") with %22. The user agent must not perform any other escapes.

Patches

As noted at the beginning of this section, encoding must be done as described in the HTML Spec.

https://html.spec.whatwg.org/#multipart-form-data

For field names and filenames for file fields, the result of the encoding in the previous bullet point must be escaped by replacing any 0x0A (LF) bytes with the byte sequence %0A, 0x0D (CR) with %0D and 0x22 (") with %22. The user agent must not perform any other escapes.

Therefore, it is recommended that Content-Disposition be modified by either of the following

Before: Content-Disposition: attachment;filename="malicious.sh";dummy=.txt

After: Content-Disposition: attachment;filename="%22malicious.sh%22;dummy=.txt"

https://github.com/jnunemaker/httparty/blob/4416141d37fd71bdba4f37589ec265f55aa446ce/lib/httparty/request/body.rb#L43

file_name.gsub('"', '%22')

Also, as for \r, \n, URL Encode is not done, but it is not newlines, so it seemed to be OK. However, since there may be omissions, it is safer to URL encode these as well, if possible. ( \r to %0A and \d to %0D )

PoC

PoC Environment

OS: macOS Monterey(12.3) Ruby ver: ruby 3.1.2p20 httparty ver: 0.20.0 (Python3 - HTTP Request Logging Server)

PoC procedure

(Linux or MacOS is required. This is because Windows does not allow file names containing " (double-quote) .)

1. Create Project

$ mkdir my-app
$ cd my-app
$ gem install httparty

2. Create malicious file

$ touch 'overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt'

3. Generate Vuln code

$ vi example.rb

require 'httparty'

filename = 'overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt'

HTTParty.post('http://localhost:12345/',
  body: {
    name: 'Foo Bar',
    email: '[email protected]',
    avatar: File.open(filename)
  }
)

4. Run Logging…

httparty before 0.21.0 is vulnerable to an assumed-immutable web parameter vulnerability. A remote and unauthenticated attacker can provide a crafted filename parameter during multipart/form-data uploads which could result in attacker controlled filenames being written.

httparty before 0.21.0 is vulnerable to an assumed-immutable web parameter vulnerability. A remote and unauthenticated attacker can provide a crafted filename parameter during multipart/form-data uploads which could result in attacker controlled filenames being written.

Impact

I found "multipart/form-data request tampering vulnerability" caused by Content-Disposition "filename" lack of escaping in httparty.

httparty/lib/httparty/request > body.rb > def generate_multipart

https://github.com/jnunemaker/httparty/blob/4416141d37fd71bdba4f37589ec265f55aa446ce/lib/httparty/request/body.rb#L43

By exploiting this problem, the following attacks are possible

• An attack that rewrites the "name" field according to the crafted file name, impersonating (overwriting) another field.
• Attacks that rewrite the filename extension at the time multipart/form-data is generated by tampering with the filename

For example, this vulnerability can be exploited to generate the following Content-Disposition.

Normal Request example: normal input filename: abc.txt

generated normal header in multipart/form-data Content-Disposition: form-data; name="avatar"; filename="abc.txt"

Malicious Request example malicious input filename: overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt

generated malicious header in multipart/form-data: Content-Disposition: form-data; name="avatar"; filename="overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt"

The Abused Header has multiple name ( avatar & foo ) fields and the "filename" has been rewritten from *.txt to *.sh .

These problems can result in successful or unsuccessful attacks, depending on the behavior of the parser receiving the request. I have confirmed that the attack succeeds, at least in the following frameworks

• Spring (Java)
• Ktor (Kotlin)
• Ruby on Rails (Ruby)

The cause of this problem is the lack of escaping of the " (Double-Quote) character in Content-Disposition > filename.

WhatWG's HTML spec has an escaping requirement.

https://html.spec.whatwg.org/#multipart-form-data

For field names and filenames for file fields, the result of the encoding in the previous bullet point must be escaped by replacing any 0x0A (LF) bytes with the byte sequence %0A, 0x0D (CR) with %0D and 0x22 (") with %22. The user agent must not perform any other escapes.

Patches

As noted at the beginning of this section, encoding must be done as described in the HTML Spec.

https://html.spec.whatwg.org/#multipart-form-data

For field names and filenames for file fields, the result of the encoding in the previous bullet point must be escaped by replacing any 0x0A (LF) bytes with the byte sequence %0A, 0x0D (CR) with %0D and 0x22 (") with %22. The user agent must not perform any other escapes.

Therefore, it is recommended that Content-Disposition be modified by either of the following

Before: Content-Disposition: attachment;filename="malicious.sh";dummy=.txt

After: Content-Disposition: attachment;filename="%22malicious.sh%22;dummy=.txt"

https://github.com/jnunemaker/httparty/blob/4416141d37fd71bdba4f37589ec265f55aa446ce/lib/httparty/request/body.rb#L43

file_name.gsub('"', '%22')

Also, as for \r, \n, URL Encode is not done, but it is not newlines, so it seemed to be OK. However, since there may be omissions, it is safer to URL encode these as well, if possible. ( \r to %0A and \d to %0D )

PoC

PoC Environment

OS: macOS Monterey(12.3) Ruby ver: ruby 3.1.2p20 httparty ver: 0.20.0 (Python3 - HTTP Request Logging Server)

PoC procedure

(Linux or MacOS is required. This is because Windows does not allow file names containing " (double-quote) .)

1. Create Project

$ mkdir my-app
$ cd my-app
$ gem install httparty

2. Create malicious file

$ touch 'overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt'

3. Generate Vuln code

$ vi example.rb

require 'httparty'

filename = 'overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt'

HTTParty.post('http://localhost:12345/',
  body: {
    name: 'Foo Bar',
    email: '[email protected]',
    avatar: File.open(filename)
  }
)

4. Run Logging…

httparty before 0.21.0 is vulnerable to an assumed-immutable web parameter vulnerability. A remote and unauthenticated attacker can provide a crafted filename parameter during multipart/form-data uploads which could result in attacker controlled filenames being written.