With pipelining enabled each incoming query on a TCP connection requires a similar resource allocation to a query received via UDP or via TCP without pipelining enabled. A client using a TCP-pipelined connection to a server could consume more resources than the server has been provisioned to handle. When a TCP connection with a large number of pipelined queries is closed, the load on the server releasing these multiple resources can cause it to become unresponsive, even for queries that can be answered authoritatively or from cache. (This is most likely to be perceived as an intermittent server problem).
Weakness
The product does not properly control the allocation and maintenance of a limited resource.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Bind | Isc | 9.11.7 (including) | 9.11.12 (including) |
| Bind | Isc | 9.14.1 (including) | 9.14.7 (including) |
| Bind | Isc | 9.15.0 (including) | 9.15.5 (including) |
| Bind | Isc | 9.11.5-s6 (including) | 9.11.5-s6 (including) |
| Bind | Isc | 9.11.6-p1 (including) | 9.11.6-p1 (including) |
| Bind | Isc | 9.11.6-rc1 (including) | 9.11.6-rc1 (including) |
| Bind | Isc | 9.11.12-s1 (including) | 9.11.12-s1 (including) |
| Bind | Isc | 9.12.4-p1 (including) | 9.12.4-p1 (including) |
| Bind | Isc | 9.12.4-p2 (including) | 9.12.4-p2 (including) |
| Red Hat Enterprise Linux 7 | RedHat | bind-32:9.11.4-16.P2.el7 | * |
| Red Hat Enterprise Linux 8 | RedHat | bind-32:9.11.13-3.el8 | * |
| Red Hat Enterprise Linux 8 | RedHat | bind-32:9.11.13-3.el8 | * |
| Bind9 | Ubuntu | bionic | * |
| Bind9 | Ubuntu | devel | * |
| Bind9 | Ubuntu | disco | * |
| Bind9 | Ubuntu | eoan | * |
| Bind9 | Ubuntu | esm-infra/bionic | * |
| Bind9 | Ubuntu | trusty | * |
Potential Mitigations
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.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/147.html
- https://cwe.mitre.org/data/definitions/227.html
- https://cwe.mitre.org/data/definitions/492.html
References
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00041.html
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00044.html
- https://kb.isc.org/docs/cve-2019-6477
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3DEMNZMKR57VQJCG5ZN55ZGTQRL2TFQ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XGURMGQHX45KR4QDRCSUQHODUFOGNGAN/
- https://support.f5.com/csp/article/K15840535?utm_source=f5support\u0026amp%3Butm_medium=RSS
- https://www.debian.org/security/2020/dsa-4689
- https://www.synology.com/security/advisory/Synology_SA_19_39
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00041.html
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00044.html
- https://kb.isc.org/docs/cve-2019-6477
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3DEMNZMKR57VQJCG5ZN55ZGTQRL2TFQ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XGURMGQHX45KR4QDRCSUQHODUFOGNGAN/
- https://support.f5.com/csp/article/K15840535?utm_source=f5support\u0026amp%3Butm_medium=RSS
- https://www.debian.org/security/2020/dsa-4689
- https://www.synology.com/security/advisory/Synology_SA_19_39