# CVE-2021-21241: CSRF can expose users authentication token in Flask-Security-Too > Attackers can steal authentication tokens via CSRF on GET endpoints, potentially taking over user accounts in Flask applications. - **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** A user has to click or open something - **Fix available:** Yes - **Published:** 11 Jan 2021 - **Updated:** 3 Aug 2024 - **Also known as:** DEBIAN-CVE-2021-21241, GHSA-hh7m-rx4f-4vpv, PYSEC-2021-91, SUSE-SU-2022:3093-1 ## What is CVE-2021-21241? CVE-2021-21241 is a high-severity vulnerability in Flask-Middleware flask-security-too, published on 11 Jan 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link. ### Official description The Python "Flask-Security-Too" package is used for adding security features to your Flask application. It is an is a independently maintained version of Flask-Security based on the 3.0.0 version of Flask-Security. In Flask-Security-Too from version 3.3.0 and before version 3.4.5, the /login and /change endpoints can return the authenticated user's authentication token in response to a GET request. Since GET requests aren't protected with a CSRF token, this could lead to a malicious 3rd party site acquiring the authentication token. Version 3.4.5 and version 4.0.0 are patched. As a workaround, if you aren't using authentication tokens - you can set the SECURITY_TOKEN_MAX_AGE to "0" (seconds) which should make the token unusable. Weakness: CWE-352 (Cross-Site Request Forgery) ## Which versions are affected by CVE-2021-21241? 3 open source packages ship an affected version, including flask-security-too and Flask-Security-Too. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `flask-security-too` | PyPI | From 3.3.0 | 3.4.5 | | `flask-security-too` | PyPI | From 3.3.0 | 3.4.5 | | `Flask-Security-Too` | PyPI | From 3.3.0 | 3.4.5 | | `python-Flask-Security-Too` | SUSE:Enterprise Storage 7 | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | SUSE:Linux Enterprise High Performance Computing 15 SP2-ESPOS | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | SUSE:Linux Enterprise Module for Basesystem 15 SP3 | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | SUSE:Linux Enterprise Module for Basesystem 15 SP4 | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | SUSE:Linux Enterprise Server 15 SP2-BCL | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | SUSE:Linux Enterprise Server 15 SP2-LTSS | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | SUSE:Linux Enterprise Server for SAP Applications 15 SP2 | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | SUSE:Manager Proxy 4.1 | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | SUSE:Manager Retail Branch Server 4.1 | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | SUSE:Manager Server 4.1 | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | openSUSE:Leap 15.3 | All versions | 3.4.2-150200.3.3.1 | | `python-Flask-Security-Too` | openSUSE:Leap 15.4 | All versions | 3.4.2-150200.3.3.1 | Products: Flask-Security-Too Project Flask-Security-Too. ## How do I fix CVE-2021-21241? Upgrade flask-security-too to 3.4.5 or later. ## Is CVE-2021-21241 being exploited? There is no known exploitation of CVE-2021-21241 in the wild and no public exploit code. ## Other vulnerabilities in Flask-Middleware flask-security-too - [CVE-2023-49438](https://insights.sbomify.com/CVE-2023-49438/): Open redirect vulnerability in Flask-Security-Too (medium 6.1) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-21241 and fix it if it is affected. What it is: CVE-2021-21241 is a high-severity vulnerability in Flask-Middleware flask-security-too, published on 11 Jan 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link. Exploitation: There is no known exploitation of CVE-2021-21241 in the wild and no public exploit code. Affected packages and fixed versions: - flask-security-too (PyPI): affected from 3.3.0; fixed in 3.4.5 - flask-security-too (PyPI): affected from 3.3.0; fixed in 3.4.5 - Flask-Security-Too (PyPI): affected from 3.3.0; fixed in 3.4.5 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2021-21241/ (Markdown: https://insights.sbomify.com/CVE-2021-21241/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-21241 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-21241 - OSV: https://osv.dev/vulnerability/CVE-2021-21241 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-21241/ Summaries are generated and may contain mistakes; the official description above is the record.