ESB-2017.2940 - [Win][UNIX/Linux] fsc (Scala compilation daemon): Execute arbitrary code/commands - Existing account 2017-11-16

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            Scala compilation daemon: Arbitrary code execution
                             16 November 2017


        AusCERT Security Bulletin Summary

Product:           fsc (Scala compilation daemon)
Publisher:         Scala
Operating System:  Windows
                   UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Execute Arbitrary Code/Commands -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2017-15288  

Original Bulletin:

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A privilege escalation vulnerability has been identified in the Scala compilation daemon.

The compile daemon is started explicitly by the `fsc` command, or implicitly by executing
a Scala source file as a script (e.g `scala MyScript.scala`). Note: Using the `scala`
command to start a REPL or to run a pre-compiled class does not start the compile daemon.

# Impact

While the compile daemon is running, an attacker with local access to the machine can
execute code as the user that started the compile daemon, and can write arbitrary
class files to any location on the filesystem that the user has access to.

# Affected Versions

  - Scala 2.1.6-2.10.6; 2.11.0-2.11.11; 2.12.0-2.12.3

# Mitigation

  - Use `scala -nocompdaemon MyScript.scala` rather than `scala MyScript.scala` to
    disable the implicit startup and use of the daemon. 
  - Avoid explicitly starting `fsc` 
  - Upgrade to Scala 2.10.7 2.11.12, 2.12.4 or higher which restricts the sensitive file to be
    readable only by the owner. These releases also change the location of the sensitive
    file: it is written in the directory `$HOME/.scalac`.


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