Amazon Linux 2023 : python3.11, python3.11-devel, python3.11-idle (ALAS2023-2026-3231)

critical Nessus Plugin ID 371869

Synopsis

The remote Amazon Linux 2023 host is missing a security update.

Description

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-3231 advisory.

When decompressing crafted zip files using the bzip/LZMA/Zstandard

compressions, Python could use an attacker-controlled size to

pre-allocate memory, possibly resulting in memory exhaustion. (CVE-2026-15310)

The HTTPPasswordMgr class in the urllib.request module, along with its subclasses HTTPPasswordMgrWithDefaultRealm and HTTPPasswordMgrWithPriorAuth, did not take the URL scheme into account when matching stored credentials against a requested URL. Credentials added for an https:// URL were also used for requests to the same host over http://, so an attacker able to redirect or downgrade a client to plain HTTP (for example, via an HTTPS-to-HTTP redirect or an on-path position) could capture credentials in cleartext. Credentials added for http:// URLs could likewise be sent over https://.

Credential matching is now scoped by URL scheme. Credentials registered with a URL that includes a scheme are only used for requests with the same scheme. Credentials registered with a bare authority (such as example.com or example.com:8080) continue to match any scheme, preserving compatibility with existing code, including proxy authentication.

Users who cannot upgrade immediately can mitigate by ensuring that applications never make plain http:// requests to hosts for which credentials are registered, for example by not following redirects to http:// URLs. (CVE-2026-15806)

The stringprep module didn't process characters from RFC 3454 tablesB.2 or B.3 correctly: the latest Unicode codepoint attributes were usedinstead of the specified Unicode 3.2.0. This behavior would causemismatches when processing domain names using IDNA 2003 (the idnacodec) and the in_table_b2() function of the stringprep module. Thisonly affects domain names containing characters that were not previouslyregistered or had their Unicode attributes such as case-foldingbehavior updated since Unicode 3.2.0. (CVE-2026-17084)

A remote, unauthenticated TLS client can make a server crash or callthrough a freed pointer if its sni_callback assigns a different context toSSLSocket.context (the documented way to select a certificate per servername) and nothing else keeps the original ssl.SSLContext alive. Typicalcases are servers that create an SSLContext per connection or replace itwhile connections are open; servers that wrap their listening socket withit are not affected.

Mitigation: keep a reference to every SSLContext that sets sni_callback forthe lifetime of the server. TLS clients are not affected. (CVE-2026-19445)

ssl.SSLContext.wrap_bio() didn't require the server_hostname argumentto not be None if ssl.SSLContext.check_hostname was set. Due to amissing parameter check in SSLObject, if the server_hostname argumentisn't supplied then hostname verification would be silently skipped.

This defect could lead to programs where certificate hostname verification*appeared* to be succeeding with SSLContext.check_hostname = True and noValueError being raised due to misconfiguration.

If the program passes a server_hostname value that isn't an empty stringor None to any of these APIs then certificate hostname verificationproceeds as expected and the program is not affected by this vulnerability.

Mitigating this vulnerability doesn't require updating Python or applyingthe patch. To mitigate, pass a valid non-None and non-emptyserver_hostname value to SSLContext.wrap_bio(),asyncio.create_connection(), or asyncio.loop.start_tls() andcertificate hostname verification will proceed as expected. Upgrading tothe latest version of Python or applying the patch only changes thebehavior from silently skipping hostname verification to raising aValueError, similar to SSLContext.wrap_socket(), when server_hostnameisn't supplied. (CVE-2026-19553)

The tarfile module's tar and dataextraction filters created directories outside the destination formembers whose name leaves the destination and returns to it, such as ../evil/../dest/sub/file. The containment check used the resolved path, but intermediate directories were created from the name as given.

Onlyempty directories are created outside the destination. Member contentsare still extracted inside it.
To return to the destination the member'sname must contain the destination directory's own final component, soextraction into a secure randomised directory is not affected.

This affects POSIX platforms only. On Windows, .. components are collapsed before the path reaches the filesystem, so the directories outside the destination are never created. (CVE-2026-19672)

In CPython 3.13 and earlier, the tarfile module's data and tar extraction filters are vulnerable to crafted archives containing a hard link to a symbolic link. Such archives may cause extraction to modify the permissions or modification time of a file outside the destination directory, or expose the contents of that file within the extracted tree. (CVE-2026-82049)

When tarfile extracts a link on a system that doesn't support links, it falls back to extracting a member from the archive. In this case, the filter function is run twice: once for the extracted member, and once with name set to the location of the link. For one of the calls, the return value was ignored. Instead, the member should be skipped if either call returns None. (CVE-2026-87910)

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 'dnf update python3.11 --releasever 2023.12.20261026' or or 'dnf update --advisory ALAS2023-2026-3231 --releasever 2023.12.20261026' to update your system.

Plugin Details

Severity: Critical

ID: 371869

File Name: al2023_ALAS2023-2026-3231.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 10/25/2026

Updated: 10/25/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.9

Percentile: 96.41

CVSS v2

Risk Factor: High

Base Score: 9.4

Temporal Score: 7

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:N

CVSS Score Source: CVE-2026-82049

CVSS v3

Risk Factor: High

Base Score: 8.1

Temporal Score: 7.1

Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

CVSS Score Source: CVE-2026-19445

CVSS v4

Risk Factor: Critical

Base Score: 9.2

Threat Score: 7.1

Threat Vector: CVSS:4.0/E:U

Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N

CVSS Score Source: CVE-2026-19445

Vulnerability Information

CPE: cpe:/o:amazon:linux:2023, p-cpe:/a:amazon:linux:python3.11-debug, p-cpe:/a:amazon:linux:python3.11-debuginfo, p-cpe:/a:amazon:linux:python3.11-debugsource, p-cpe:/a:amazon:linux:python3.11-devel, p-cpe:/a:amazon:linux:python3.11-idle, p-cpe:/a:amazon:linux:python3.11-libs, p-cpe:/a:amazon:linux:python3.11-test, p-cpe:/a:amazon:linux:python3.11-tkinter, p-cpe:/a:amazon:linux:python3.11

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 10/24/2026

Vulnerability Publication Date: 8/18/2026

Reference Information

CVE: CVE-2026-15310, CVE-2026-15806, CVE-2026-17084, CVE-2026-19445, CVE-2026-19553, CVE-2026-19672, CVE-2026-82049, CVE-2026-87910

IAVA: 2026-A-0890

Detections

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