CVE-2021-27913 is a low-severity (CVSS 3.5) Broken Cryptographic Algorithm vulnerability in mautic/core. 1 public exploit reference exists, so weaponization risk is real. A fix is available for mautic/core — see the affected versions and patch details below.
Use of a Broken or Risky Cryptographic Algorithm
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-27913 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
mautic/core🐘mautic/coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
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
- https://openwall.com/php_mt_seedhttps://crypto.di.uoa.gr/CRYPTO.SEC/Randomness_Attacks_files/paper.pdf
- https://github.com/mautic/mautic/blob/5213e320b4ef4d0c51bb84c1d46a1071e8e4f7fc/app/bundles/PointBundle/Controller/TriggerController.php#L187
- https://github.com/mautic/mautic/releases/tag/3.3.4
- https://github.com/mautic/mautic/releases/tag/4.0.0
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | mautic/core | all versions | 3.3.4composer require mautic/core:^3.3.4 |
| 🐘Packagist | mautic/core | ≥ 4.0.0-alpha1&&< 4.0.0 | 4.0.0composer require mautic/core:^4.0.0 |
Affected Products
mauticacquiaResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mautic/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mautic/core to 3.3.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-27913 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2021-27913 in your dependencies?
Find it across Packagist, including transitive dependencies.