CVE-2025-13836 Excessive read buffering DoS in http.client
Medium 6.3
Published
Updated
Check this codebase for CVE-2025-13836 and fix it if it is affected.
What it is: CVE-2025-13836 is a medium-severity denial of service vulnerability in Python Python, published on 1 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-13836 in the wild and no public exploit code.
Affected packages and fixed versions:
- libpython (Bitnami): affected all versions; fixed in 3.10.20, 3.11.15, 3.12.13, 3.13.11, 3.14.1
- python (Bitnami): affected all versions; fixed in 3.10.20, 3.11.15, 3.12.13, 3.13.11, 3.14.1
- python-min (Bitnami): affected all versions; fixed in 3.10.20, 3.11.15, 3.12.13, 3.13.11, 3.14.1
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-2025-13836/ (Markdown: https://insights.sbomify.com/CVE-2025-13836/index.md)
A malicious server can cause a Python HTTP client to exhaust memory by sending large responses, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-13836?
CVE-2025-13836 is a medium-severity denial of service vulnerability in Python Python, published on 1 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
When reading an HTTP response from a server, if no read amount is specified, the default behavior will be to use Content-Length. This allows a malicious server to cause the client to read large amounts of data into memory, potentially causing OOM or other DoS.
Weakness: CWE-400
Which versions are affected by CVE-2025-13836?
3 open source packages ship an affected version, including libpython, python and python-min. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
libpython Bitnami | All versions | 3.10.20, 3.11.15, 3.12.13, 3.13.11, 3.14.1 |
python Bitnami | All versions | 3.10.20, 3.11.15, 3.12.13, 3.13.11, 3.14.1 |
python-min Bitnami | All versions | 3.10.20, 3.11.15, 3.12.13, 3.13.11, 3.14.1 |
Linux distribution packages (37)
python3.12 AlmaLinux:8 | All versions | 3.12.12-2.el8_10 |
python3.12-debug AlmaLinux:8 | All versions | 3.12.12-2.el8_10 |
python3.12-devel AlmaLinux:8 | All versions | 3.12.12-2.el8_10 |
python3.12-idle AlmaLinux:8 | All versions | 3.12.12-2.el8_10 |
python3.12-libs AlmaLinux:8 | All versions | 3.12.12-2.el8_10 |
python3.12-rpm-macros AlmaLinux:8 | All versions | 3.12.12-2.el8_10 |
python3.12-test AlmaLinux:8 | All versions | 3.12.12-2.el8_10 |
python3.12-tkinter AlmaLinux:8 | All versions | 3.12.12-2.el8_10 |
python3.12 Red Hat:enterprise_linux:8::appstream | All versions | 0:3.12.12-2.el8_10 |
python3.12-debuginfo Red Hat:enterprise_linux:8::appstream | All versions | 0:3.12.12-2.el8_10 |
python3.12-debugsource Red Hat:enterprise_linux:8::appstream | All versions | 0:3.12.12-2.el8_10 |
python3.12-devel Red Hat:enterprise_linux:8::appstream | All versions | 0:3.12.12-2.el8_10 |
python3.12-libs Red Hat:enterprise_linux:8::appstream | All versions | 0:3.12.12-2.el8_10 |
python3.12-rpm-macros Red Hat:enterprise_linux:8::appstream | All versions | 0:3.12.12-2.el8_10 |
python3.12-tkinter Red Hat:enterprise_linux:8::appstream | All versions | 0:3.12.12-2.el8_10 |
python3.12 Red Hat:enterprise_linux:8::crb | All versions | 0:3.12.12-2.el8_10 |
python3.12-debug Red Hat:enterprise_linux:8::crb | All versions | 0:3.12.12-2.el8_10 |
python3.12-debuginfo Red Hat:enterprise_linux:8::crb | All versions | 0:3.12.12-2.el8_10 |
python3.12-debugsource Red Hat:enterprise_linux:8::crb | All versions | 0:3.12.12-2.el8_10 |
python3.12-idle Red Hat:enterprise_linux:8::crb | All versions | 0:3.12.12-2.el8_10 |
python3.12-test Red Hat:enterprise_linux:8::crb | All versions | 0:3.12.12-2.el8_10 |
python3.12-tkinter Red Hat:enterprise_linux:8::crb | All versions | 0:3.12.12-2.el8_10 |
python3.12 Red Hat:rhel_eus:9.4::appstream | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-debuginfo Red Hat:rhel_eus:9.4::appstream | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-debugsource Red Hat:rhel_eus:9.4::appstream | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-devel Red Hat:rhel_eus:9.4::appstream | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-libs Red Hat:rhel_eus:9.4::appstream | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-tkinter Red Hat:rhel_eus:9.4::appstream | All versions | 0:3.12.1-4.el9_4.10 |
python3.12 Red Hat:rhel_eus:9.4::crb | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-debug Red Hat:rhel_eus:9.4::crb | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-debuginfo Red Hat:rhel_eus:9.4::crb | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-debugsource Red Hat:rhel_eus:9.4::crb | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-idle Red Hat:rhel_eus:9.4::crb | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-test Red Hat:rhel_eus:9.4::crb | All versions | 0:3.12.1-4.el9_4.10 |
python3.12-tkinter Red Hat:rhel_eus:9.4::crb | All versions | 0:3.12.1-4.el9_4.10 |
python3.12 Red Hat:rhel_eus:9.6::appstream | All versions | 0:3.12.9-1.el9_6.5 |
python3.12-debuginfo Red Hat:rhel_eus:9.6::appstream | All versions | 0:3.12.9-1.el9_6.5 |
Products include Python Python.
How do I fix CVE-2025-13836?
Upgrade libpython to a fixed version for your release line: 3.10.20, 3.11.15, 3.12.13 or 3.13.11.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-13836 being exploited?
There is no known exploitation of CVE-2025-13836 in the wild and no public exploit code.
Other vulnerabilities in Python Python
Sources
Also known as ALSA-2026:2419, AZL-109689, AZL-71264, BELL-CVE-2025-13836, BIT-libpython-2025-13836, BIT-python-2025-13836 and 18 more.