# CVE-2021-23336: Web Cache Poisoning > Attackers can poison web caches by exploiting semicolon parameter parsing differences in Python's urllib, leading to security bypasses. - **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:H/E:P/RL:U/RC:C`) - **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:** 15 Feb 2021 - **Updated:** 14 Oct 2026 - **Also known as:** ALPINE-CVE-2021-23336, AZL-109632, AZL-6827, AZL-84275, BIT-django-2021-23336, BIT-libpython-2021-23336, BIT-python-2021-23336, BIT-python-min-2021-23336, CLEANSTART-2026-JK29834, CVE-2020-28476, DEBIAN-CVE-2021-23336, DLA-2569-1, GHSA-4qjw-vx62-3vqx, MGASA-2021-0135, MGASA-2021-0165, OESA-2021-1125, PSF-2021-1, SNYK-UPSTREAM-PYTHONCPYTHON-1074933, SUSE-SU-2021:0768-1, SUSE-SU-2021:0886-1, SUSE-SU-2021:0887-1, SUSE-SU-2021:0947-1, UBUNTU-CVE-2021-23336, USN-4742-1, openSUSE-SU-2021:0435-1, openSUSE-SU-2024:11279-1, openSUSE-SU-2024:12893-1, openSUSE-SU-2024:14037-1, openSUSE-SU-2026:11948-1 ## What is CVE-2021-23336? CVE-2021-23336 is a medium-severity vulnerability in Debian Debian Linux, published on 15 Feb 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 package python/cpython from 0 and before 3.6.13, from 3.7.0 and before 3.7.10, from 3.8.0 and before 3.8.8, from 3.9.0 and before 3.9.2 are vulnerable to Web Cache Poisoning via urllib.parse.parse_qsl and urllib.parse.parse_qs by using a vector called parameter cloaking. When the attacker can separate query parameters using a semicolon (;), they can cause a difference in the interpretation of the request between the proxy (running with default configuration) and the server. This can result in malicious requests being cached as completely safe ones, as the proxy would usually not see the semicolon as a separator, and therefore would not include it in a cache key of an unkeyed parameter. Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests) ## Which versions are affected by CVE-2021-23336? 4 open source packages ship an affected version, including django, libpython and python. It affects 12 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `django` | Bitnami | From 2.2.0 | 2.2.19, 3.0.13, 3.1.7 | | `libpython` | Bitnami | All versions | 3.6.13, 3.7.10, 3.8.8, 3.9.2 | | `python` | Bitnami | All versions | 3.6.13, 3.7.10, 3.8.8, 3.9.2 | | `python-min` | Bitnami | All versions | 3.6.13, 3.7.10, 3.8.8, 3.9.2 | | `python` | SUSE:Enterprise Storage 6 | All versions | 2.7.18-7.55.1 | | `python-base` | SUSE:Enterprise Storage 6 | All versions | 2.7.18-7.55.1 | | `python` | SUSE:Linux Enterprise High Performance Computing 15 SP1-ESPOS | All versions | 2.7.18-7.55.1 | | `python-base` | SUSE:Linux Enterprise High Performance Computing 15 SP1-ESPOS | All versions | 2.7.18-7.55.1 | | `python` | SUSE:Linux Enterprise High Performance Computing 15 SP1-LTSS | All versions | 2.7.18-7.55.1 | | `python-base` | SUSE:Linux Enterprise High Performance Computing 15 SP1-LTSS | All versions | 2.7.18-7.55.1 | | `python` | SUSE:Linux Enterprise High Performance Computing 15-ESPOS | All versions | 2.7.18-7.55.1 | | `python-base` | SUSE:Linux Enterprise High Performance Computing 15-ESPOS | All versions | 2.7.18-7.55.1 | | `python` | SUSE:Linux Enterprise High Performance Computing 15-LTSS | All versions | 2.7.18-7.55.1 | | `python-base` | SUSE:Linux Enterprise High Performance Computing 15-LTSS | All versions | 2.7.18-7.55.1 | | `python3` | SUSE:Linux Enterprise Micro 5.0 | All versions | 3.6.13-3.78.1 | | `python3-core` | SUSE:Linux Enterprise Micro 5.0 | All versions | 3.6.13-3.78.1 | | `python` | SUSE:Linux Enterprise Module for Basesystem 15 SP2 | All versions | 2.7.18-7.55.1 | | `python-base` | SUSE:Linux Enterprise Module for Basesystem 15 SP2 | All versions | 2.7.18-7.55.1 | | `python3` | SUSE:Linux Enterprise Module for Basesystem 15 SP2 | All versions | 3.6.13-3.78.1 | | `python3-core` | SUSE:Linux Enterprise Module for Basesystem 15 SP2 | All versions | 3.6.13-3.78.1 | | `python` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP2 | All versions | 2.7.18-7.55.1 | | `python3-core` | SUSE:Linux Enterprise Module for Development Tools 15 SP2 | All versions | 3.6.13-3.78.1 | | `python` | SUSE:Linux Enterprise Module for Python 2 15 SP2 | All versions | 2.7.18-7.55.1 | | `python-base` | SUSE:Linux Enterprise Module for Python 2 15 SP2 | All versions | 2.7.18-7.55.1 | | `python3` | SUSE:Linux Enterprise Module for Web and Scripting 12 | All versions | 3.4.10-25.66.1 | | `python3-base` | SUSE:Linux Enterprise Module for Web and Scripting 12 | All versions | 3.4.10-25.66.1 | | `python3` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 3.4.10-25.66.1 | | `python3-base` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 3.4.10-25.66.1 | | `python36` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 3.6.13-4.36.1 | | `python36-core` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 3.6.13-4.36.1 | | `python` | SUSE:Linux Enterprise Server 15 SP1-BCL | All versions | 2.7.18-7.55.1 | | `python-base` | SUSE:Linux Enterprise Server 15 SP1-BCL | All versions | 2.7.18-7.55.1 | | `python` | SUSE:Linux Enterprise Server 15 SP1-LTSS | All versions | 2.7.18-7.55.1 | | `python-base` | SUSE:Linux Enterprise Server 15 SP1-LTSS | All versions | 2.7.18-7.55.1 | | `python` | SUSE:Linux Enterprise Server 15-LTSS | All versions | 2.7.18-7.55.1 | | `python-base` | SUSE:Linux Enterprise Server 15-LTSS | All versions | 2.7.18-7.55.1 | | `python3` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 3.4.10-25.66.1 | | `python3-base` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 3.4.10-25.66.1 | | `python36` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 3.6.13-4.36.1 | | `python36-core` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 3.6.13-4.36.1 | Products: Debian Debian Linux, Djangoproject Django, Fedoraproject Fedora, Netapp Cloud Backup, Netapp Inventory Collect Tool, Netapp Ontap Select Deploy Administration Utility, Netapp Snapcenter, Oracle Communications Offline Mediation Controller, Oracle Communications Pricing Design Center, Oracle Enterprise Manager Ops Center, Oracle Zfs Storage Appliance, Python Python. ## How do I fix CVE-2021-23336? Upgrade django to a fixed version for your release line: 2.2.19, 3.0.13 or 3.1.7. ## Is CVE-2021-23336 being exploited? There is no known exploitation of CVE-2021-23336 in the wild and no public exploit code. ## Other vulnerabilities in Debian Debian Linux - [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild) - [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild) - [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild) - [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild) - [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-23336 and fix it if it is affected. What it is: CVE-2021-23336 is a medium-severity vulnerability in Debian Debian Linux, published on 15 Feb 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-2021-23336 in the wild and no public exploit code. Affected packages and fixed versions: - django (Bitnami): affected from 2.2.0; fixed in 2.2.19, 3.0.13, 3.1.7 - libpython (Bitnami): affected all versions; fixed in 3.6.13, 3.7.10, 3.8.8, 3.9.2 - python (Bitnami): affected all versions; fixed in 3.6.13, 3.7.10, 3.8.8, 3.9.2 - python-min (Bitnami): affected all versions; fixed in 3.6.13, 3.7.10, 3.8.8, 3.9.2 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-2021-23336/ (Markdown: https://insights.sbomify.com/CVE-2021-23336/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-23336 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-23336 - OSV: https://osv.dev/vulnerability/CVE-2021-23336 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-23336/ Summaries are generated and may contain mistakes; the official description above is the record.