OpenSSH Information for VU#368819

Double Free Bug in zlib Compression Library Corrupts malloc's Internal Data Structures



Vendor Statement

OpenSSH itself relies on zlib as a third party library. OpenSSH's internal malloc state might get corrupted if the double-free bug is present in zlib. At this moment, it is not known if this bug will allow an intruder to gain privileges.

For some malloc implementation it is possible to detect and ignore the double-free. However, that is entirely dependent on the malloc implementation. Currently, it seems that *BSD operating systems might not be affected by this problem.

We advise everybody to upgrade their third party libraries and recompile OpenSSH if necessary. Turning off compression in the server is possible only by removing zlib from myproposal.h and subsequent recompliation.

Index: myproposal.h
RCS file: /cvs/src/usr.bin/ssh/myproposal.h,v
retrieving revision 1.13
diff -u -r1.13 myproposal.h
--- myproposal.h        21 Jan 2002 22:30:12 -0000      1.13
+++ myproposal.h        12 Mar 2002 17:36:11 -0000
@@ -32,7 +32,7 @@
       "hmac-md5,hmac-sha1,hmac-ripemd160," \
       "," \
-#define        KEX_DEFAULT_COMP        "none,zlib"
!)+#define        KEX_DEFAULT_COMP        "none"
#define        KEX_DEFAULT_LANG        ""

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Vendor References



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