The mod_proxy_ajp module in the Apache HTTP Server before 2.2.21, when used with mod_proxy_balancer in certain configurations, allows remote attackers to cause a denial of service (temporary error state in the backend server) via a malformed HTTP request.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Http_server | Apache | 2.2.12 (including) | 2.2.20 (including) |
| Red Hat Enterprise Linux 6 | RedHat | httpd-0:2.2.15-9.el6_1.3 | * |
| Red Hat JBoss Enterprise Web Server 1 for RHEL 5 | RedHat | httpd-0:2.2.17-15.4.ep5.el5 | * |
| Red Hat JBoss Enterprise Web Server 1 for RHEL 6 | RedHat | httpd-0:2.2.17-15.4.ep5.el6 | * |
| Red Hat JBoss Web Server 1.0 | RedHat | * | |
| Apache2 | Ubuntu | hardy | * |
| Apache2 | Ubuntu | lucid | * |
| Apache2 | Ubuntu | maverick | * |
| Apache2 | Ubuntu | natty | * |
| Apache2 | Ubuntu | oneiric | * |
| Apache2 | Ubuntu | upstream | * |
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.