Jinja is an extensible templating engine. Prior to 3.1.6, an oversight in how the Jinja sandboxed environment interacts with the |attr filter allows an attacker that controls the content of a template to execute arbitrary Python code. To exploit the vulnerability, an attacker needs to control the content of a template. Whether that is the case depends on the type of application using Jinja. This vulnerability impacts users of applications which execute untrusted templates. Jinja's sandbox does catch calls to str.format and ensures they don't escape the sandbox. However, it's possible to use the |attr filter to get a reference to a string's plain format method, bypassing the sandbox. After the fix, the |attr filter no longer bypasses the environment's attribute lookup. This vulnerability is fixed in 3.1.6.
A flaw was found in Jinja. In affected versions, an oversight in how the Jinja sandboxed environment interacts with the `|attr` filter allows an attacker who controls the content of a template to execute arbitrary Python code. To exploit the vulnerability, an attacker needs to control the content of a template. Whether that is the case depends on the type of application using Jinja. This vulnerability impacts users of applications that execute untrusted templates. Jinja's sandbox does catch calls to `str.format` and ensures they don't escape the sandbox. However, it's possible to use the `|attr` filter to get a reference to a string's plain format method, bypassing the sandbox.
Rafal Krupinski discovered that Jinja2 did not properly restrict the execution of code in situations where templates are used maliciously. An attacker with control over a template's filename and content could potentially use this issue to enable the execution of arbitrary code. This issue only affected Ubuntu 14.04 LTS and Ubuntu 16.04 LTS. It was discovered that Jinja2 sandboxed environments could be escaped through a call to a string format method. An attacker could possibly use this issue to enable the execution of arbitrary code. This issue only affected Ubuntu 14.04 LTS and Ubuntu 16.04 LTS.
