[EEYEB-20060524] Symantec Remote Management Stack Buffer Overflow Jun 12 2006 10:25PM
eEye Advisories (Advisories eeye com)
Symantec Remote Management Stack Buffer Overflow

Release Date:
June 12, 2006

Date Reported:
May 24, 2006

High (Remote Code Execution)

Systems Affected:
Symantec AntiVirus 10.0.x for Windows (all versions)
Symantec AntiVirus 10.1.x for Windows (all versions)
Symantec Client Security 3.0.x for Windows (all versions)
Symantec Client Security 3.1.x for Windows (all versions)

Systems Not Affected:
Symantec AntiVirus 10.x.x for Macintosh
Symantec AntiVirus 10.x.x for Linux
Symantec AntiVirus 10.x.x for Wireless

eEye Digital Security has discovered a vulnerability in the remote
management interface for Symantec AntiVirus 10.x and Symantec Client
Security 3.x, which could be exploited by an anonymous attacker in order
to execute arbitrary code with SYSTEM privileges on an affected system.
The management interface is typically enabled in enterprise settings and
listens on TCP port 2967 by default, for both server and client systems.

Although remote management traffic is typically SSL-encrypted, managed
systems will accept and process clear-text requests of the vulnerable

Technical Details:
The remote management protocol communicated by the affected products is
a proprietary message-based protocol with two levels of encapsulation.
The outer layer comprises a message header indicating one of three
message types: 10, which designates a request to Rtvscan.exe, or 20 or
30, which mediate SSL negotiation. If SSL is established for a TCP
connection, subsequent traffic is encrypted although the plaintext is
still in the proprietary format.

The data of type-10 messages contains its own header and body which are
processed by Rtvscan.exe. This header features a command field which
specifies the operation to perform and dictates the format of the body

The COM_FORWARD_LOG (0x24) command handler contains an improper use of
strncat that allows a 0x180-byte stack buffer to be overflowed with
arbitrary data. If the first string in the COM_FORWARD_LOG request body
contains a backslash, then one of the following two strncat calls will
be performed:

* If the string contains a comma but no double-quote:

strncat(dest, src, 0x17A - strlen(src));

* Otherwise:

strncat(dest, src, 0x17C - strlen(src));

If the length of the source string exceeds 0x17A or 0x17C characters
respectively, the arithmetic will underflow and result in a very large
copy size (since the copy size argument is of type size_t, which is
unsigned). This causes the entire source string to be appended to the
buffer, allowing the stack to be overwritten with up to 64KB of data in
which only null characters are prohibited.

Rtvscan.exe was compiled with the Visual Studio /GS security option
which institutes stack canary checks, but this security measure can be
bypassed by causing a very large overwrite and taking control of an
exception handler registration.

As a basic workaround against automated exploitation, the management
interface TCP port may be changed via the
gentIPPort" registry value in order to accomplish a very slight amount
of obfuscation. Remote management should continue to function even if
the new port numbers are not homogeneous across an enterprise.

Retina Network Security Scanner has been updated to identify this
Blink - Endpoint Vulnerability Prevention - preemptively protects from
this vulnerability.

Vendor Status:
Symantec has released patches for the affected products. For more
information, please consult Symantec security advisory SYM06-010:

Note that the installation of one or more previous patches may be
required before the SYM06-010 patch can be applied.

This issue has been assigned CVE-2006-2630.

Derek Soeder

Related Links:
Retina Network Security Scanner - Free Trial
Blink Endpoint Vulnerability Prevention - Free Trial

Symantec engineers, for very quickly producing a solid patch. Family
and friends. Anti-greets to copperhead snakes.

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