Bug 844442 - (CVE-2012-3440) CVE-2012-3440 sudo: insecure temporary file use in RPM %postun script
CVE-2012-3440 sudo: insecure temporary file use in RPM %postun script
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Red Hat Product Security
: Security
Depends On: 844443 844444
Blocks: 841858
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Reported: 2012-07-30 12:15 EDT by Tomas Hoger
Modified: 2015-07-31 05:01 EDT (History)
3 users (show)

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Doc Type: Bug Fix
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Last Closed: 2012-08-07 13:43:54 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description Tomas Hoger 2012-07-30 12:15:32 EDT
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 12:54:03 EDT
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

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