Bug 844442 (CVE-2012-3440) - CVE-2012-3440 sudo: insecure temporary file use in RPM %postun script
Summary: CVE-2012-3440 sudo: insecure temporary file use in RPM %postun script
Alias: CVE-2012-3440
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
Depends On: 844443 844444
Blocks: 841858
TreeView+ depends on / blocked
Reported: 2012-07-30 16:15 UTC by Tomas Hoger
Modified: 2019-09-29 12:54 UTC (History)
3 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2012-08-07 17:43:54 UTC

Attachments (Terms of Use)

System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2012:1149 0 normal SHIPPED_LIVE Moderate: sudo security and bug fix update 2012-08-07 20:52:26 UTC

Description Tomas Hoger 2012-07-30 16:15:32 UTC
The sudo packages in Red Hat Enterprise Linux 5 contained a %postun script (executed during the package removal or upgrade) that created a temporary file insecurely.  The script did the following:

# Remove the "sudoers:" line from nsswitch.conf if it's not modified
if grep -q "^sudoers: files ldap$" ""/etc/nsswitch.conf""; then
   rm -f ""/var/tmp/nsswitch.conf.bak"" && \
   touch ""/var/tmp/nsswitch.conf.bak"" && \
   grep -v "^sudoers: files ldap$" ""/etc/nsswitch.conf"" > ""/var/tmp/nsswitch.conf.bak"" && \
   mv -f ""/var/tmp/nsswitch.conf.bak"" ""/etc/nsswitch.conf""

There was a race condition between the removal of the temporary file and its re-creation using touch.  A local attacker could possibly use this to create nsswitch.conf.bak file or symlink after rm -f "/var/tmp/nsswitch.conf.bak" was run and cause the script to overwrite arbitrary file with the contents of the /etc/nsswitch.conf file, or make the script create /etc/nsswitch.conf file with attacker controlled content and permissions.  The attack would have to be executed during the sudo package upgrade or removal.

This problem was introduced in the sudo erratum RHSA-2012:0309 which was released in Red Hat Enterprise Linux 5.8:


The sudo packages in other Red Hat Enterprise Linux versions did not include this %postun script and were not affected this issue.

Comment 2 errata-xmlrpc 2012-08-07 16:54:03 UTC
This issue has been addressed in following products:

  Red Hat Enterprise Linux 5

Via RHSA-2012:1149 https://rhn.redhat.com/errata/RHSA-2012-1149.html

Note You need to log in before you can comment on or make changes to this bug.