# CVE-2026-97689: urllib3: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory > A malicious HTTP server can cause memory exhaustion in urllib3 clients by sending an unbounded chunk-size line, leading to denial of service. - **Severity:** High 8.9 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 29 Sep 2026 - **Updated:** 29 Sep 2026 - **Also known as:** ALSA-2026:90759, AZL-105660, AZL-105915, BELL-CVE-2026-97689, CLEANSTART-2026-DB54467, CLEANSTART-2026-DZ64581, CLEANSTART-2026-EH65259, CLEANSTART-2026-IL95812, CLEANSTART-2026-IQ88986, CLEANSTART-2026-KW58831, CLEANSTART-2026-OX34995, DEBIAN-CVE-2026-97689, ECHO-ba49-d64e-7a3d, GHSA-vxq7-64xx-v4gw, MINI-243c-922m-xw5h, MINI-2rxx-8h32-x67v, MINI-366w-rgc3-5rj7, MINI-3v4r-hrvh-hx3p, MINI-4frx-mcxf-4h9q, MINI-4hm5-4pj2-mpm5, MINI-5892-69p7-95cc, MINI-78jj-9grf-v487, MINI-7qf5-m9cq-3g89, MINI-92rx-p24f-574q, MINI-9c9q-prc5-2566, MINI-fcqr-4749-x36j, MINI-ffj4-962h-28q2, MINI-fmjh-p5mv-r97x, MINI-g74v-9mwp-qvf2, MINI-gfjw-7g37-hhqq, MINI-h7mc-v2m2-vchp, MINI-hvvc-g6vh-4r3m, MINI-j5xq-x57m-xc8r, MINI-j779-9pj6-c3pg, MINI-jf58-8g8p-6vw9, MINI-jh7w-xpwm-g2qw, MINI-m565-j2gv-v9wh, MINI-m82x-rm6f-28rc, MINI-mh9m-mmfh-338f, MINI-pjg6-pmg7-f7w9, MINI-prhq-v572-2jpp, MINI-q2f9-qhjj-f538, MINI-rj72-rv5h-8q47, MINI-rv66-7xx5-j6p5, MINI-w7rx-pq56-627q, MINI-wc8j-mjpx-765x, MINI-x36r-jcq3-hxv2, MINI-x558-pqwv-2xgj, OESA-2026-4501, OESA-2026-4502, OESA-2026-4503, PYSEC-2026-4177, RLSA-2026:90759, ROOT-APP-PYPI-CVE-2026-97689, UBUNTU-CVE-2026-97689 ## What is CVE-2026-97689? CVE-2026-97689 is a high-severity denial of service vulnerability in urllib3, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description urllib3 is an HTTP client library for Python. From 1.10.3 until 2.8.0, the HTTPResponse.read_chunked and HTTPResponse.stream methods can allocate unbounded memory because the streaming chunk parser buffers the chunk-size field until newline or EOF without a length bound. The trigger is that a malicious server returns Transfer-Encoding: chunked followed by a very long run of bytes without a newline. The attack mechanism is that a malicious HTTP server sends a very long unterminated chunk-size line. The impact is that unbounded memory allocation can exhaust the client process. This issue is fixed in version 2.8.0. Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling) ## Which versions are affected by CVE-2026-97689? 3 open source packages ship an affected version, including urllib3. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `urllib3` | PyPI | From 1.10.3 | 2.8.0 | | `urllib3` | PyPI | From 1.10.3 | 2.8.0 | | `urllib3` | PyPI | From 1.10.3 | 2.8.0 | | `python3-urllib3` | AlmaLinux:8 | All versions | 1.24.2-11.el8_10 | | `python-urllib3` | Rocky Linux:8 | All versions | 0:1.24.2-11.el8_10 | Products: Python Urllib3. ## How do I fix CVE-2026-97689? Upgrade urllib3 to 2.8.0 or later. ## Is CVE-2026-97689 being exploited? There is no known exploitation of CVE-2026-97689 in the wild and no public exploit code. ## Other vulnerabilities in urllib3 - [CVE-2026-44432](https://insights.sbomify.com/CVE-2026-44432/): urllib3: Decompression-bomb safeguards bypassed in parts of the streaming API (high 8.9) - [CVE-2026-21441](https://insights.sbomify.com/CVE-2026-21441/): urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API) (high 8.9) - [CVE-2025-66418](https://insights.sbomify.com/CVE-2025-66418/): urllib3 allows an unbounded number of links in the decompression chain (high 8.9) - [CVE-2025-66471](https://insights.sbomify.com/CVE-2025-66471/): urllib3 Streaming API improperly handles highly compressed data (high 8.9) - [CVE-2026-44431](https://insights.sbomify.com/CVE-2026-44431/): urllib3: Sensitive headers forwarded across origins in proxied low-level redirects (high 8.2) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-97689 and fix it if it is affected. What it is: CVE-2026-97689 is a high-severity denial of service vulnerability in urllib3, published on 29 Sep 2026. 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-2026-97689 in the wild and no public exploit code. Affected packages and fixed versions: - urllib3 (PyPI): affected from 1.10.3; fixed in 2.8.0 - urllib3 (PyPI): affected from 1.10.3; fixed in 2.8.0 - urllib3 (PyPI): affected from 1.10.3; fixed in 2.8.0 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-2026-97689/ (Markdown: https://insights.sbomify.com/CVE-2026-97689/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97689 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97689 - OSV: https://osv.dev/vulnerability/CVE-2026-97689 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-97689/ Summaries are generated and may contain mistakes; the official description above is the record.