SB2020012222 - Denial of service in Trustwave ModSecurity

Description

This security bulletin contains information about 2 vulnerabilities.

1) Input validation error (CVE-ID: CVE-2019-19886)

CWE-ID: CWE-20 - Improper input validation

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input in "Transaction::addRequestHeader" in transaction.cc. A remote attacker can send specially crafted crafted requests to the server and cause a denial of service condition on the target system.

2) Improper handling of exceptional conditions (CVE-ID: CVE-2019-25043)

CWE-ID: CWE-755 - Improper Handling of Exceptional Conditions

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to improper handling of errors while parsing key-value pair. A remote attacker can send a specially crafted header to the server and perform a denial of service (DoS) attack, as demonstrated by a "string index out of range" error and worker-process crash for a "Cookie: =abc" header.

Remediation

Install update from vendor's website.

References

• https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/modsecurity-denial-of-service-details-cve-2019-19886/
• https://github.com/SpiderLabs/ModSecurity/issues/2566