Summary
Use of a Broken or Risky Cryptographic Algorithm
✍️ 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
Impact
The application uses a cryptographic algorithm known to have weaknesses, such as MD5, SHA-1, or DES. Typical impact: compromised confidentiality or integrity of protected data.
CVE-2021-27913 has a CVSS score of 3.5 (Low). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.3.4, 4.0.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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mautic/core to 3.3.4 or later; mautic/core to 4.0.0 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2021-27913? CVE-2021-27913 is a low-severity use of a broken or risky cryptographic algorithm vulnerability in mautic/core (composer), affecting versions < 3.3.4. It is fixed in 3.3.4, 4.0.0. The application uses a cryptographic algorithm known to have weaknesses, such as MD5, SHA-1, or DES.
- How severe is CVE-2021-27913? CVE-2021-27913 has a CVSS score of 3.5 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of mautic/core are affected by CVE-2021-27913? mautic/core (composer) versions < 3.3.4 is affected.
- Is there a fix for CVE-2021-27913? Yes. CVE-2021-27913 is fixed in 3.3.4, 4.0.0. Upgrade to this version or later.
- Is CVE-2021-27913 exploitable, and should I be worried? Whether CVE-2021-27913 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-27913 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-27913?
- Upgrade
mautic/coreto 3.3.4 or later - Upgrade
mautic/coreto 4.0.0 or later
- Upgrade