ActionScript Sound Class Cross-Origin Information Disclosure

vendor:

N/A

by:

Google Security Research

7.5

CVSS

HIGH

Information Disclosure

200

CWE

Product Name: N/A

Affected Version From: N/A

Affected Version To: N/A

Patch Exists: No

Related CWE: N/A

CPE: N/A

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: N/A

2015

ActionScript Sound Class Cross-Origin Information Disclosure

An instance of ActionScript's Sound class allows for loading and extracting for further processing any kind of external data, not only sound files. Same-origin policy doesn't apply here. Each input byte of raw data, loaded previously from given URL, is encoded by an unspecified function to the same 8 successive sample blocks of output. The sample block consists of 8 bytes (first 4 bytes for left channel and next 4 bytes for right channel). Only 2 bytes from 8 sound blocks (64 bytes) are crucial, the rest 52 bytes are useless. Each byte of input from range 0-255 has corresponding constant unsigned integer value (a result of encoding), so for decoding purposes you can use simply lookup table (cf. source code from BoundlessTunes.as). Put attached file BoundlessTunes.swf on the HTTP server. Open http://<SERVER_HOSTNAME>/BoundlessTunes.swf?url=<URL> where <URL> is an URL address (e.g. leading to cross-origin resource). A received response will be displayed in alert window.

Mitigation:

Ensure that the Sound class is not used to load external data.

Source

Exploit-DB raw data:

Source: https://code.google.com/p/google-security-research/issues/detail?id=354&can=1&q=label%3AProduct-Flash%20modified-after%3A2015%2F8%2F17&sort=id

[90-day deadline tracking for https://code.google.com/p/chromium/issues/detail?id=481639]

---
An instance of ActionScript's Sound class allows for loading and extracting for further processing any kind of external data, not only sound files. Same-origin policy doesn't apply here. Each input byte of raw data, loaded previously from given URL, is encoded by an unspecified function to the same 8 successive sample blocks of output. The sample block consists of 8 bytes (first 4 bytes for left channel and next 4 bytes for right channel). Only 2 bytes from 8 sound blocks (64 bytes) are crucial, the rest 52 bytes are useless. Each byte of input from range 0-255 has corresponding constant unsigned integer value (a result of encoding), so for decoding purposes you can use simply lookup table (cf. source code from BoundlessTunes.as).

1. Put attached file BoundlessTunes.swf on the HTTP server.
2. Open http://<SERVER_HOSTNAME>/BoundlessTunes.swf?url=<URL> where <URL> is an URL address (e.g. leading to cross-origin resource). A received response will be displayed in alert window.
---

Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/37851.zip