CVE-2025-27516: Jinja sandbox breakout through attr filter selecting format method
Description
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.
Classification
CVE ID: CVE-2025-27516
CVSS Base Severity: MEDIUM
CVSS Base Score: 5.4
CVSS Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Affected Products
Vendor: pallets
Product: jinja
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.07% (probability of being exploited)
EPSS Percentile: 17.2% (scored less or equal to compared to others)
EPSS Date: 2025-04-02 (when was this score calculated)
Stakeholder-Specific Vulnerability Categorization (SSVC)
SSVC Exploitation: none
SSVC Technical Impact: partial
SSVC Automatable: true
References
https://nvd.nist.gov/vuln/detail/CVE-2025-27516https://github.com/pallets/jinja/security/advisories/GHSA-cpwx-vrp4-4pq7
https://github.com/pallets/jinja/commit/90457bbf33b8662926ae65cdde4c4c32e756e403