Secunia Research: Link Grammar "separate_sentence()" Buffer Overflow

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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
individuals, who are interested in or concerned about IT-security.

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:

http://corporate.secunia.com/secunia_research/33/

Secunia regularly hires new skilled team members. Check the URL below
to see currently vacant positions:

http://secunia.com/secunia_vacancies/

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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