-----BEGIN PGP SIGNED MESSAGE-----
AUSCERT External Security Bulletin Redistribution
ESB-2003.0540 -- OpenBSD Security Advisory
off-by-one error in realpath(3)
05 August 2003
AusCERT Security Bulletin Summary
Product: libc function: realpath(3)
Operating System: OpenBSD 3.3 and prior
Impact: Denial of Service
Execute Arbitrary Code/Commands
- --------------------------BEGIN INCLUDED TEXT--------------------
An off-by-one error exists in the C library function realpath(3).
This is the same bug that was recently found in the wu-ftpd ftpd
server by Janusz Niewiadomski and Janusz Niewiadomski.
The OpenBSD ftp daemon does not use realpath(3) in a way that could
be exploited, however a number of other system binaries also use
the function. It is not currently known whether or not this bug
results in an exploitable security hole on OpenBSD. Since the bug
led to an exploitable hole in wu-ftpd, it is entirely possible that
some program using realpath(3) under OpenBSD may be vulnerable to
attack. For OpenBSD 3.3 and higher, the ProPolice stack protector
should provide some protection from this bug, but this cannot be
This bug has been fixed in OpenBSD-current as well as the 3.2 and
3.3 stable branches. Patches are available for OpenBSD 3.2 and 3.3.
Patch for OpenBSD 3.2:
Patch for OpenBSD 3.3:
For versions of OpenBSD prior to 3.2, users may simply fetch
the current revision of realpath.c from:
then rebuild and install libc with the new realpath.c.
For more details, see the description of the wu-ftpd fp_realpath bug:
- --------------------------END INCLUDED TEXT--------------------
You have received this e-mail bulletin as a result of your organisation's
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to firstname.lastname@example.org
and we will forward your request to the appropriate person.
This security bulletin is provided as a service to AusCERT's members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.
NOTE: This is only the original release of the security bulletin. It may
not be updated when updates to the original are made. If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.
Contact information for the authors of the original document is included
in the Security Bulletin above. If you have any questions or need further
information, please contact them directly.
Previous advisories and external security bulletins can be retrieved from:
If you believe that your computer system has been compromised or attacked in
any way, we encourage you to let us know by completing the secure National IT
Incident Reporting Form at:
Internet Email: email@example.com
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business
hours which are GMT+10:00 (AEST). On call after hours
for member emergencies only.
-----BEGIN PGP SIGNATURE-----
-----END PGP SIGNATURE-----