CVE-2020-8616

A malicious actor who intentionally exploits this lack of effective limitation on the number of fetches performed when processing referrals can, through the use of specially crafted referrals, cause a recursing server to issue a very large number of fetches in an attempt to process the referral. This has at least two potential effects: The performance of the recursing server can potentially be degraded by the additional work required to perform these fetches, and The attacker can exploit this behavior to use the recursing server as a reflector in a reflection attack with a high amplification factor.

Weakness

The product does not properly control the allocation and maintenance of a limited resource.

Affected Software

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
• http://www.nxnsattack.com
• http://www.openwall.com/lists/oss-security/2020/05/19/4
• https://kb.isc.org/docs/cve-2020-8616
• https://lists.debian.org/debian-lts-announce/2020/05/msg00031.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JKJXVBOKZ36ER3EUCR7VRB7WGHIIMPNJ/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WOGCJS2XQ3SQNF4W6GLZ73LWZJ6ZZWZI/
• https://security.netapp.com/advisory/ntap-20200522-0002/
• https://usn.ubuntu.com/4365-1/
• https://usn.ubuntu.com/4365-2/
• https://www.debian.org/security/2020/dsa-4689
• https://www.synology.com/security/advisory/Synology_SA_20_12
• http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00041.html
• http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00044.html
• http://www.nxnsattack.com
• http://www.openwall.com/lists/oss-security/2020/05/19/4
• https://kb.isc.org/docs/cve-2020-8616
• https://lists.debian.org/debian-lts-announce/2020/05/msg00031.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JKJXVBOKZ36ER3EUCR7VRB7WGHIIMPNJ/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WOGCJS2XQ3SQNF4W6GLZ73LWZJ6ZZWZI/
• https://security.netapp.com/advisory/ntap-20200522-0002/
• https://usn.ubuntu.com/4365-1/
• https://usn.ubuntu.com/4365-2/
• https://www.debian.org/security/2020/dsa-4689
• https://www.synology.com/security/advisory/Synology_SA_20_12