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                     Secunia Research 07/11/2007

          - Link Grammar "separate_sentence()" Buffer Overflow -

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Table of Contents

Affected Software....................................................1
Severity.............................................................2
Vendor's Description of Software.....................................3
Description of Vulnerability.........................................4
Solution.............................................................5
Time Table...........................................................6
Credits..............................................................7
References...........................................................8
About Secunia........................................................9
Verification........................................................10

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1) Affected Software 

* Link Grammar 4.1b.

NOTE: Other versions may also be affected.

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2) Severity 

Rating: Moderately critical
Impact: System access
Where:  Remote

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3) Vendor's Description of Software 

"The Link Grammar Parser is a syntactic parser of English, based on
link grammar, an original theory of English syntax. Given a sentence,
the system assigns to it a syntactic structure, which consists of a 
set of labeled links connecting pairs of words. The parser also 
produces a "constituent" representation of a sentence (showing noun 
phrases, verb phrases, etc.)"

Product Link:
http://www.link.cs.cmu.edu/link/

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4) Description of Vulnerability

Secunia Research has discovered a vulnerability in Link Grammar, which
can be exploited by malicious people to compromise an application 
using the affected code.

The vulnerability is caused due to a boundary error within the
"separate_word()" function in tokenize.c when processing overly long
words (over 61 bytes). This can be exploited to cause a stack-based
buffer overflow via a specially crafted sentence passed to the
"separate_sentence()" function.

Successful exploitation allows execution of arbitrary code.

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5) Solution 

Do not parse untrusted text using the affected function.

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6) Time Table 

23/10/2007 - Vendor notified.
07/11/2007 - Public disclosure.

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7) Credits 

Discovered by Alin Rad Pop, Secunia Research.

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8) References

The Common Vulnerabilities and Exposures (CVE) project has assigned 
CVE-2007-5395 for the vulnerability.

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9) About Secunia

Secunia offers vulnerability management solutions to corporate
customers with verified and reliable vulnerability intelligence
relevant to their specific system configuration:

http://corporate.secunia.com/

Secunia also provides a publicly accessible and comprehensive advisory
database as a service to the security community and private 
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http://secunia.com/

Secunia believes that it is important to support the community and to
do active vulnerability research in order to aid improving the 
security and reliability of software in general:

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Secunia regularly hires new skilled team members. Check the URL below
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Secunia offers a FREE mailing list called Secunia Security Advisories:

http://secunia.com/secunia_security_advisories/ 

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10) Verification 

Please verify this advisory by visiting the Secunia website:
http://secunia.com/secunia_research/2007-78/

Complete list of vulnerability reports published by Secunia Research:
http://secunia.com/secunia_research/

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