# CVE-2026-44432: urllib3 — Fixed in 2.7.0 🐍 PyPI Not in CISA KEV # CVE-2026-44432 — urllib3 CVE-2026-44432 is a CWE-409 vulnerability in urllib3. A fix is available for urllib3 — see the affected versions and patch details below. urllib3: Decompression-bomb safeguards bypassed in parts of the streaming API Also known as[GHSA-mf9v-mfxr-j63j](/vulnerability/GHSA-mf9v-mfxr-j63j)PYSEC-2026-142 Published May 13, 2026 Updated Oct 28, 2026 Affected 1 pkg Patched 1 / 1 Exploits None indexed Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS) ## Exploitation Status ### No confirmed exploitation observed yet - CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment. Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44432. ## EPSS Exploitation Probability [via FIRST.org ↗](https://www.first.org/epss/) 0.7%probability of exploitation in next 30 days Lower Risk\-0.20% Lower risk than most CVEs53th percentile — riskier than 53% of all scored CVEsHighest risk 0.18%0.58%0.98%1.38%0.7%0.7%0.7%0.9%0.7%Jul 26Sep 26Nov 26 Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/). ## Real-World Exposure 1 pkg affected 🐍`urllib3` Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems. ## Description #### Impact urllib3's [streaming API](https://urllib3.readthedocs.io/en/2.7.0/advanced-usage.html#streaming-and-i-o) is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once. urllib3 can perform decompression based on the HTTP `Content-Encoding` header (e.g., `gzip`, `deflate`, `br`, or `zstd`). When using the streaming API since version 2.6.0, the library decompresses only the necessary bytes, enabling partial content consumption. However, urllib3 before version 2.7.0 could still decompress the whole response instead of the requested portion in two cases: 1. During the second `HTTPResponse.read(amt=N)` call when the response was decompressed using the official [Brotli](https://pypi.org/project/brotli/) library. 2. When `HTTPResponse.drain_conn()` was called after the response had been read and decompressed partially (compression algorithm did not matter here). These issues could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This could result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data; CWE-409) on the client side. #### Affected usages Applications and libraries using urllib3 versions earlier than 2.7.0 may be affected when streaming compressed responses from untrusted sources in either of these cases, unless decompression is explicitly disabled: 1. A response encoded with `br` is read incrementally with at least two `HTTPResponse.read(amt=N)` or `HTTPResponse.stream(amt=N)` calls while using the official [Brotli](https://pypi.org/project/brotli/) library. 2. `HTTPResponse.drain_conn()` is called after response decompression has already started. #### Remediation Upgrade to at least urllib3 version 2.7.0 in which the library: 1. Is more efficient for reads with Brotli. 2. Always skips decompression for `HTTPResponse.drain_conn()`. If upgrading is not immediately possible, the following workarounds may reduce exposure in specific cases: 1. For the Brotli-specific issue only, switch from [brotli](https://pypi.org/project/brotli/) to [brotlicffi](https://pypi.org/project/brotlicffi/) until you can upgrade urllib3; the official Brotli package is affected because of [https://github.com/google/brotli/issues/1396](https://github.com/google/brotli/issues/1396). 2. If your code explicitly calls `HTTPResponse.drain_conn()`, call `HTTPResponse.close()` instead when connection reuse is not important. #### Credits The Brotli-specific issue was reported by @kimkou2024. `HTTPResponse.drain_conn()` inefficiency was reported by @Cycloctane. ## Affected Packages 1 total 1 fixed Ecosystem Package Vulnerable range Fix 🐍PyPI `urllib3` ≥ 2.6.0&&< 2.7.0 2.7.0`pip install --upgrade 'urllib3==2.7.0'` ## Affected Products 1 product · 1 configurations Application `urllib3`python ≥ 2.6.0 && < 2.7.0 range ## Detection & mitigation playbook Open-source dependency 1. ### Detect Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for urllib3, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version. 2. ### Fix Update urllib3 to 2.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44432 is resolved across your whole dependency graph. 3. ### Workarounds Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service. ## Fixing This On Your OS If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project. Red HatImportant Product Fixed in Advisory Red Hat Ansible Automation Platform 2.5 for RHEL 8 `automation-controller-0:4.6.30-2.el8ap` [RHSA-2026:42078](https://access.redhat.com/errata/RHSA-2026:42078) Red Hat Ansible Automation Platform 2.6 for RHEL 9 `python3.12-urllib3-0:2.7.0-1.el9ap` [RHSA-2026:34160](https://access.redhat.com/errata/RHSA-2026:34160) Red Hat Ansible Automation Platform 2.6 for RHEL 9 `automation-controller-0:4.7.14-3.el9ap` [RHSA-2026:42079](https://access.redhat.com/errata/RHSA-2026:42079) Red Hat Enterprise Linux 10 `python3.14-urllib3-0:2.6.3-2.el10_2` [RHSA-2026:27929](https://access.redhat.com/errata/RHSA-2026:27929) Red Hat Enterprise Linux 10 `python-urllib3-0:1.26.19-4.el10_2` [RHSA-2026:28000](https://access.redhat.com/errata/RHSA-2026:28000) Red Hat Enterprise Linux 8 `python3.12-urllib3-0:1.26.19-3.el8_10` [RHSA-2026:32992](https://access.redhat.com/errata/RHSA-2026:32992) Red Hat Enterprise Linux 9 `python3.14-urllib3-0:2.6.3-2.el9_8` [RHSA-2026:28157](https://access.redhat.com/errata/RHSA-2026:28157) Red Hat Enterprise Linux 9 `python3.12-urllib3-0:1.26.19-3.el9_8` [RHSA-2026:28159](https://access.redhat.com/errata/RHSA-2026:28159) ## Frequently Asked Questions \### Impact urllib3's \[streaming API\](https://urllib3.readthedocs.io/en/2.7.0/advanced-usage.html#streaming-and-i-o) is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once. urllib3 can perform decompression based on the HTTP \`Content-Encoding\` header (e.g., \`gzip\`, \`deflate\`, \`br\`, or \`zstd\`). When using the streaming API since version 2.6.0, the library decompresses only the necessary bytes, enabling partial content consumption. However, urllib3 before version 2.7.0 could still decompr O3 Security · Impact-Aware SCA ### Is CVE-2026-44432 in your dependencies? Find it across PyPI, including transitive dependencies. [Scan my dependencies](/book-demo) [How O3 SCA works](/impact-aware-sca)