A flaw was found in the way Bash evaluated certain specially crafted environment variables. An attacker could use this flaw to override or bypass environment restrictions to execute shell commands. Certain services and applications allow remote unauthenticated attackers to provide environment variables, allowing them to exploit this issue.
We'd like to also give credit to our colleagues at Red Hat for their excellent blog post summarizing this issue.
Run yum update bash to update your system.
i686: bash-doc-4.1.2-15.19.amzn1.i686 bash-4.1.2-15.19.amzn1.i686 bash-debuginfo-4.1.2-15.19.amzn1.i686 src: bash-4.1.2-15.19.amzn1.src x86_64: bash-4.1.2-15.19.amzn1.x86_64 bash-debuginfo-4.1.2-15.19.amzn1.x86_64 bash-doc-4.1.2-15.19.amzn1.x86_64