Detections
Analytics
Amazon Linux 2 : python3-urllib3, --advisory ALAS2-2026-3127 (ALAS-2026-3127)
high Nessus Plugin ID 294890
Synopsis
The remote Amazon Linux 2 host is missing a security update.Description
The version of python3-urllib3 installed on the remote host is prior to 1.25.6-2. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2026-3127 advisory.urllib3 is a user-friendly HTTP client library for Python. When using urllib3's proxy support with `ProxyManager`, the `Proxy-Authorization` header is only sent to the configured proxy, as expected.
However, when sending HTTP requests *without* using urllib3's proxy support, it's possible to accidentally configure the `Proxy-Authorization` header even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat the `Proxy- Authorization` HTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects. Because this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the `Proxy-Authorization` header during cross-origin redirects to avoid the small chance that users are doing this on accident. Users should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the `Proxy-Authorization` header, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach. We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited: 1. Setting the `Proxy-Authorization` header without using urllib3's built-in proxy support. 2. Not disabling HTTP redirects. 3. Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin. Users are advised to update to either version 1.26.19 or version 2.2.2. Users unable to upgrade may use the `Proxy-Authorization` header with urllib3's `ProxyManager`, disable HTTP redirects using `redirects=False` when sending requests, or not user the `Proxy-Authorization` header as mitigations. (CVE-2024-37891)
urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.24 and prior to 2.6.0, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data. This vulnerability is fixed in 2.6.0. (CVE-2025-66418)
urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.0 and prior to 2.6.0, the Streaming API improperly handles highly compressed data. urllib3's streaming API 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. When streaming a compressed response, urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd).
The library must read compressed data from the network and decompress it until the requested chunk size is met. Any resulting decompressed data that exceeds the requested amount is held in an internal buffer for the next read operation. The decompression logic could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This can result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data. (CVE-2025-66471)
Tenable has extracted the preceding description block directly from the tested product security advisory.
Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.
Solution
Run 'yum update python3-urllib3' or or 'yum update --advisory ALAS2-2026-3127' to update your system.See Also
https://alas.aws.amazon.com//AL2/ALAS2-2026-3127.html
https://alas.aws.amazon.com/faqs.html
https://explore.alas.aws.amazon.com/CVE-2024-37891.html
Plugin Details
Severity: High
ID: 294890
File Name: al2_ALAS-2026-3127.nasl
Version: 1.1
Type: local
Agent: unix
Published: 1/21/2026
Updated: 1/21/2026
Supported Sensors: Nessus Agent, Continuous Assessment, Nessus
Risk Information
VPR
Risk Factor: Medium
Score: 4.4
CVSS v2
Risk Factor: Medium
Base Score: 6.8
Temporal Score: 5.3
Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:N/A:N
CVSS Score Source: CVE-2024-37891
CVSS v3
Risk Factor: Medium
Base Score: 6.5
Temporal Score: 5.9
Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C
CVSS v4
Risk Factor: High
Base Score: 8.9
Threat Score: 7.7
Threat Vector: CVSS:4.0/E:P
Vector: 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
CVSS Score Source: CVE-2025-66471
Vulnerability Information
CPE: cpe:/o:amazon:linux:2, p-cpe:/a:amazon:linux:python3-urllib3
Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list
Exploit Available: true
Exploit Ease: Exploits are available
Patch Publication Date: 1/21/2026
Vulnerability Publication Date: 6/17/2024