Skip to content

Use of a Broken or Risky Cryptographic Algorithm

Low
RCheesley published GHSA-x7g2-wrrp-r6h3 Aug 30, 2021

Package

mautic/core (PHP)

Affected versions

< 3.3.4, < 4.0.0-rc

Patched versions

3.3.4, 4.0.0

Description

✍️ Description

The function mt_rand is used to generate session tokens, this function is cryptographically flawed due to its nature being one pseudorandomness, an attacker can take advantage of the cryptographically insecure nature of this function to enumerate session tokens for accounts that are not under his/her control

🕵️‍♂️ Proof of Concept

Numerous examples and attack implementations can be found in this paper . If you're looking for a practical tool that can crack your mt_rand implementation's seed value, see this project and run the following commands in a console with php5 and OpenWall's tool installed:

root$ php -r 'mt_srand(13333337); echo mt_rand( ), "\n";'
After that, copy the output (1863134308) and execute the following commands:

root$ gcc php_mt_seed.c -o php_mt_seedroot$ ./php_mt_seed 1863134308
After waiting ~1 minute you should have a few possible seeds corresponding to their PHP versions, next to your installed PHP version you should see something akin to:

seed = 0x00cb7359 = 13333337 (PHP 7.1.0+)
Hey, that's your seed!

💥 Impact

An attacker could takeover accounts at random by enumerating and using access tokens.

📝 References

Severity

Low
3.5
/ 10

CVSS base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:L

CVE ID

CVE-2021-27913

Weaknesses

Credits