CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:N/I:N/A:P
EPSS
Percentile
82.1%
Incorrect decoding of malformed DNS packets causes certain DNS implementations to hang or crash.
RFC1035 (DOMAIN NAMES, IMPLEMENTATION AND SPECIFICATION) defines a mechanism for conserving bytes in a DNS query or reply packet by avoiding repetition of character strings (“labels”) in a domain name. Thus if the label “domain.com” appears several times in a query or response packet (i.e. “www.domain.com”, “host.subdomain.domain.com”, “ns.domain.com”), only the first occurrence need be fully specified - further occurrences of “domain.com” can be alluded to by using a pointer to the first occurrence. Since labels in a DNS packet are preceded by an 8 bit length field, and since individual labels are restricted to 63 characters, there are 2 unused bits in the length field. Setting these two bits 2 to “11” indicates that the following byte is not a label but rather a pointer to a prior occurrence of a label elsewhere in the packet. Programs are not required to encode packets using this label compression scheme, but all programs are required to be able to decode any such packets that are received.
Numerous DNS implementations do not perform sufficient input checking on compressed labels, allowing an attacker to craft a DNS query containing malformed compressed labels. For example, a packet can be constructed that has a pointer that points back to itself, or that contains a pointer that points to another pointer which points back to the first pointer. When vulnerable programs attempt to decode these malformed labels, various undesirable effects can be induced in the decoding process including allocating all of the process’s available memory or causing the process to enter an infinite loop.
Note: Any program that performs raw decoding of DNS packets (sniffers, IDS, nameservers, etc.) may potentially exhibit this vulnerability unless care has been taken in the implementation of the decompression code. Many popular programs besides tcpdump and ethereal perform these functions, and may not have been tested for this vulnerability yet.
If a remote, unauthenticated attacker supplies a vulnerable DNS implementation with a specially crafted query, they may be able to cause that DNS software to enter an infinite loop eventually consuming 100% CPU resources. This will cause the DNS software to crash resulting in a denial-of-service condition.
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Users are encouraged to check with their vendor to determine the appropriate patch or update to apply.
23495
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Updated: May 30, 2001
Affected
Upgrade to at least ethereal 0.8.7
The vendor has not provided us with any further information regarding this vulnerability.
The CERT/CC has no additional comments at this time.
If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%2323495 Feedback>).
Updated: May 30, 2001
Affected
Upgrade to at least tcpdump 3.5
The vendor has not provided us with any further information regarding this vulnerability.
The CERT/CC has no additional comments at this time.
If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%2323495 Feedback>).
Updated: November 10, 2005
Not Affected
We have not received a statement from the vendor.
The vendor has not provided us with any further information regarding this vulnerability.
Notified: November 10, 2005 Updated: November 15, 2005
Not Affected
According to Microsoft:
The Microsoft implementation of DNS is not affected.
The vendor has not provided us with any further information regarding this vulnerability.
Notified: November 10, 2005 Updated: November 10, 2005
Unknown
We have not received a statement from the vendor.
The vendor has not provided us with any further information regarding this vulnerability.
Notified: November 10, 2005 Updated: November 10, 2005
Unknown
We have not received a statement from the vendor.
The vendor has not provided us with any further information regarding this vulnerability.
Notified: November 10, 2005 Updated: November 10, 2005
Unknown
We have not received a statement from the vendor.
The vendor has not provided us with any further information regarding this vulnerability.
Group | Score | Vector |
---|---|---|
Base | ||
Temporal | ||
Environmental |
Thanks to Hugo Breton and [email protected] for reporting this vulnerability. Additional information for this issue was provided by the by the NISCC Vulnerability Management Team.
This document was written by the CERT Technical Staff.
CVE IDs: | CVE-2000-0333 |
---|---|
Severity Metric: | 41.92 Date Public: |
secunia.com/advisories/15472/
www.ciac.org/ciac/bulletins/l-015.shtml
www.cisco.com/warp/public/707/cisco-sn-20050524-dns.shtml
www.ethereal.com
www.niscc.gov.uk/niscc/docs/al-20050524-00433.html
www.securityfocus.com/bid/1165
www.securityfocus.com/bid/13729
www.securitytracker.com/id?1014043
www.securitytracker.com/id?1014044
www.securitytracker.com/id?1014045
www.securitytracker.com/id?1014046
www.tcpdump.org