CVE-2026-44432 - High Severity Vulnerability
Vulnerable Library - urllib3-2.6.3-py3-none-any.whl
HTTP library with thread-safe connection pooling, file post, and more.
Library home page: https://files.pythonhosted.org/packages/39/08/aaaad47bc4e9dc8c725e68f9d04865dbcb2052843ff09c97b08904852d84/urllib3-2.6.3-py3-none-any.whl
Path to dependency file: /requirements.txt
Path to vulnerable library: /tmp/ws-ua_20260402140528_BYRDYW/python_TYRXAX/20260402140530/urllib3-2.6.3-py3-none-any.whl,/tmp/ws-ua_20260402140528_BYRDYW/python_TYRXAX/20260402140530/urllib3-2.6.3-py3-none-any.whl
Dependency Hierarchy:
- ❌ urllib3-2.6.3-py3-none-any.whl (Vulnerable Library)
Found in HEAD commit: 733821ba208032bbe0d8b2992a2e4aece4265119
Found in base branch: main
Vulnerability Details
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: 3. 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. 4. "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: 5. Is more efficient for reads with Brotli. 6. Always skips decompression for "HTTPResponse.drain_conn()". If upgrading is not immediately possible, the following workarounds may reduce exposure in specific cases: 7. 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 google/brotli#1396. 8. 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.
Publish Date: 2026-05-11
URL: CVE-2026-44432
CVSS 3 Score Details (8.6)
Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: None
- User Interaction: None
- Scope: Changed
- Impact Metrics:
- Confidentiality Impact: None
- Integrity Impact: None
- Availability Impact: High
For more information on CVSS3 Scores, click here.
Suggested Fix
Type: Upgrade version
Origin: GHSA-mf9v-mfxr-j63j
Release Date: 2026-05-11
Fix Resolution: urllib3 - 2.7.0,urllib3 - 2.7.0
Step up your Open Source Security Game with Mend here
CVE-2026-44432 - High Severity Vulnerability
HTTP library with thread-safe connection pooling, file post, and more.
Library home page: https://files.pythonhosted.org/packages/39/08/aaaad47bc4e9dc8c725e68f9d04865dbcb2052843ff09c97b08904852d84/urllib3-2.6.3-py3-none-any.whl
Path to dependency file: /requirements.txt
Path to vulnerable library: /tmp/ws-ua_20260402140528_BYRDYW/python_TYRXAX/20260402140530/urllib3-2.6.3-py3-none-any.whl,/tmp/ws-ua_20260402140528_BYRDYW/python_TYRXAX/20260402140530/urllib3-2.6.3-py3-none-any.whl
Dependency Hierarchy:
Found in HEAD commit: 733821ba208032bbe0d8b2992a2e4aece4265119
Found in base branch: main
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: 3. 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. 4. "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: 5. Is more efficient for reads with Brotli. 6. Always skips decompression for "HTTPResponse.drain_conn()". If upgrading is not immediately possible, the following workarounds may reduce exposure in specific cases: 7. 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 google/brotli#1396. 8. 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.
Publish Date: 2026-05-11
URL: CVE-2026-44432
Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: None
- User Interaction: None
- Scope: Changed
- Impact Metrics:
- Confidentiality Impact: None
- Integrity Impact: None
- Availability Impact: High
For more information on CVSS3 Scores, click here.Type: Upgrade version
Origin: GHSA-mf9v-mfxr-j63j
Release Date: 2026-05-11
Fix Resolution: urllib3 - 2.7.0,urllib3 - 2.7.0
Step up your Open Source Security Game with Mend here