Red Hat Bugzilla – Bug 164928
CAN-2005-2475 TOCTOU issue in unzip
Last modified: 2007-11-30 17:11:11 EST
+++ This bug was initially created as a clone of Bug #164927 +++
This issue was posted to bugtraq by Imran Ghory
If a malicious local user has write access to a directory in which a
target user is using unzip to extract a file to then a
TOCTOU bug can be exploited to change the permission of any file
belonging to that user.
On decompressing unzip copies the permissions from the compressed
file to the uncompressed file. However there is a gap between the
uncompressed file being written (and it's file handler being close)
and the permissions of the file being changed.
During this gap a malicious user can remove the decompressed file and
replace it with a hard-link to another file belonging to the user.
unzip will then change the permissions on the hard-linked file to be
the same as that of the compressed file.
The vulnerable line of code can be found on line 1160 of the file
unix.c where chmod is used (rather than fchmod). unzip also use's
chmod in a number of other places which may also be vulnerable to
This issue should also affect FC3
This bug is fixed in devel (5.51-12).