Missing Required Cryptographic Step Leading to Sensitive Information Disclosure in TYPO3 CMS

> ### Meta
> * CVSS: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C (8.2)
> * CWE-325, CWE-20, CWE-200, CWE-502

Problem

It has been discovered that an internal verification mechanism can be used to generate arbitrary checksums. This allows to inject arbitrary data having a valid cryptographic message authentication code (HMAC-SHA1) and can lead to various attack chains as described below.

• TYPO3-CORE-SA-2020-007, CVE-2020-15099: Potential Privilege Escalation
  • the database server used for a TYPO3 installation must be accessible for an attacker (either via internet or shared hosting network)
  • CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C (7.5, high)
• TYPO3-CORE-SA-2016-013, CVE-2016-5091: Insecure Deserialization & Remote Code Execution
  • an attacker must have access to at least one Extbase plugin or module action in a TYPO3 installation
  • CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C (9.1, critical)

The overall severity of this vulnerability is high (8.2) based on mentioned attack chains and the requirement of having a valid backend user session (authenticated).

Solution

Update to TYPO3 versions 9.5.20 or 10.4.6 that fix the problem described.

Credits

Thanks to TYPO3 security team member Oliver Hader who reported and fixed the issue.

References

• TYPO3-CORE-SA-2020-008