EEYE: Symantec Multiple Firewall DNS Response Denial-of-Service
Symantec Multiple Firewall DNS Response Denial-of-Service
Release Date:
May 12, 2004
Date Reported:
April 19, 2004
Severity:
High (Remote Denial of Service)
Vendor:
Symantec
Systems Affected:
Symantec Norton Internet Security 2002
Symantec Norton Internet Security 2003
Symantec Norton Internet Security 2004
Symantec Norton Internet Security Professional 2002
Symantec Norton Internet Security Professional 2003
Symantec Norton Internet Security Professional 2004
Symantec Norton Personal Firewall 2002
Symantec Norton Personal Firewall 2003
Symantec Norton Personal Firewall 2004
Symantec Client Firewall 5.01, 5.1.1
Symantec Client Security 1.0, 1.1, 2.0(SCF 7.1)
Symantec Norton AntiSpam 2004
Description:
eEye Digital Security has discovered a second vulnerability in the
Symantec firewall product line that can be remotely exploited to cause a
severe denial-of-service condition on systems running a default
installation of an affected version of the product. By sending a single
malicious DNS (UDP port 53) response packet to a vulnerable host, an
attacker can cause the Symantec DNS response validation code to enter an
infinite loop within the kernel, amounting to a system freeze that
requires the machine to be physically rebooted in order to restore
operation.
Technical Description:
The SYMDNS.SYS driver included in these products validates each DNS
response packet before allowing it through the firewall, attempting to
reassemble a DNS answer name into a single dotted string as part of this
process. Although not as hot as Barns's and Karl's stack overflow in the
same routine, there is also a denial-of-service vulnerability in the
name component concatention code involving the processing of compressed
name pointers (name component with a length byte >= 40h, as far as
SYMDNS is concerned, followed by the offset of the name component to
substitute in place of the pointer). Specifically, if a compressed name
pointer is constructed that points to itself, this routine will loop
infinitely as it forever follows the compressed name pointer, to the
compressed name pointer, to the compressed name pointer...
The following is a DNS response packet containing such a pointer:
Offset Size Data Description
------- ------- --------------- --------------------------------
0000h WORD xx xx Transaction ID
0002h WORD 80 00 Flags (bit 15: response)
0004h WORD 00 01 Number of questions
0006h WORD 00 01 Number of answer RRs
0008h WORD xx xx Number of authority RRs
000Ah WORD xx xx Number of additional RRs
000Ch WORD C0 0C Compressed name pointer to itself
By sending an attack packet to any open UDP port on a vulnerable system,
from a source port of 53, the vulnerable code will be reached and the
denial-of-service condition will occur.
Protection:
Retina Network Security Scanner has been updated to identify this
vulnerability.
Vendor Status:
Symantec has released a patch for this vulnerability. The patch is
available via the Symantec LiveUpdate service. For more information
please refer to the Symantec security advisory.
http://securityresponse.symantec.com/avcenter/security/Content/2004.05.1
2.html
Credit:
Discovery: Barnaby Jack, Karl Lynn, Derek Soeder
Related Links:
Retina Network Security Scanner - Free 15 Day Trial
http://www.eeye.com/html/Products/Retina/download.html
Greetings:
D12/2, Ink, AiC, "Screenshot guy"(tm), and we would also like to thank
our contact Mike over at Symantec for being patient and cooperative
throughout the reporting process.
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