FERRAMENTAS LINUX: Urgent Fedora 42 Security Update: Python 3.13.12 Patches 7 Critical Command Injection Flaws

Urgent Fedora 42 Security Update: Python 3.13.12 patches 7 critical vulnerabilities including CVE-2026-0672 (HTTP cookie injection) and CVE-2025-15366 (IMAP command injection). Discover the full scope of these high-risk flaws, their potential for RCE and data breaches, and the exact DNF commands to secure your enterprise Linux systems against active exploits. Complete advisory inside.

The Fedora Project has released an urgent security update for python3.13 (version 3.13.12) addressing a cluster of seven high-severity vulnerabilities.

These flaws, primarily centered on command and header injection, expose unpatched Fedora 42 systems to potential remote code execution (RCE), data exfiltration, and session hijacking.

This advisory dissects the technical nuances of these CVEs, explains the specific risks to enterprise environments, and provides the exact remediation commands required to harden your infrastructure.

Failure to patch immediately could allow attackers to compromise email servers, manipulate web application headers, and execute arbitrary commands via seemingly benign inputs.

Executive Summary: The Scope of the Python 3.13 Vulnerabilities

The updates address critical weaknesses in how Python’s standard library handles untrusted data. The vulnerabilities span multiple core modules, from email and web headers to mail protocols (IMAP/POP3).

Key Risk Vectors Exploited:

Protocol Injection: Attackers can inject malicious commands into IMAP and POP3 sessions.
HTTP Header Smuggling: Flaws in http.cookies.Morsel and wsgiref allow newline injection, leading to cache poisoning or cross-site scripting (XSS).
Data URL Manipulation: Improper filtering in data URL mediatypes opens doors to obfuscated attacks.

Deep Dive: Analyzing the 7 Critical CVEs

To understand the urgency, one must look beyond the patch notes. These aren't theoretical bugs; they are active attack vectors in modern web and mail infrastructures. Below is a technical breakdown of the most critical threats neutralized in this update.

The 'Morsel' Menace: CVE-2026-0672 (HTTP Cookie Injection)

Severity: High | CVSS Vector: Network exploitable
This vulnerability resides in the http.cookies.Morsel object. By injecting carriage return and line feed (CRLF) characters into a cookie value, an attacker can effectively split an HTTP response. This allows them to set arbitrary headers or even craft malicious content that the browser interprets as part of a different response, leading to cache poisoning and session fixation.

Expert Insight: "This is a classic case of assuming input validation occurs downstream. The Morsel object failed to sanitize newlines, effectively handing attackers the keys to poison web caches and hijack user sessions." — Analysis based on Red Hat Bugzilla #2431792.

Mail Server Compromise: CVE-2025-15366 & CVE-2025-15367 (IMAP/POP3 Injection)

Severity: Critical | Affected Modules: imaplib, poplib
These vulnerabilities allow for command injection when user-controlled data is passed to the IMAP and POP3 libraries. An attacker who can control part of an email address or mailbox name could terminate the intended command and execute arbitrary commands on the mail server.

Practical Example: An application using user input to construct an IMAP SEARCH command could be exploited. Instead of searching for an email, the attacker injects \r\n followed by a malicious command like RENAME or DELETE, potentially wiping mailboxes.

The 'Newline' Plague: CVE-2026-0865 & CVE-2025-15282 (Header Injection)

Severity: High | Affected Modules: wsgiref.headers, urllib.parse
The WSGI reference implementation (wsgiref.headers.Headers) was found to allow header injection via newlines. Simultaneously, a similar flaw was discovered in how urllib.parse handles newlines within the mediatype of data URLs.

Security Implication: For applications using WSGI, this could allow response splitting. In urllib, malformed data URLs could bypass security filters, leading to XSS or open redirects.

The Bigger Picture: Why This Python Update is Non-Negotiable

Ignoring this update means leaving your digital infrastructure porous. The common thread in these CVEs is injection—the OWASP Top 10's most prevalent class of vulnerabilities. Attackers are constantly scanning for systems running outdated Python stacks, specifically targeting Fedora machines in CI/CD pipelines and web server roles.

By updating to 3.13.12, you are not just applying a version bump; you are fundamentally closing the door on a family of injection attacks that could lead to total system compromise.

Immediate Remediation: Patching Your Fedora 42 Systems

The fix requires updating the python3.13 package to version 3.13.12-1.fc42. This is a straightforward process using the dnf package manager. Prioritize patching systems exposed to the internet, including web servers, mail servers, and developer workstations.

Step-by-Step Update Instructions:

Open a terminal on your Fedora 42 system.

Execute the upgrade command with root privileges:

sudo dnf upgrade --advisory FEDORA-2026-b1b37b00ef

Verify the installation:
bash
```
python3.13 --version
```
The output should display Python 3.13.12.
Restart affected services (web servers, application daemons) to ensure the new Python runtime is loaded.

Frequently Asked Questions (FAQ)

Q: Is my application automatically safe after updating Python?

A: The Python interpreter is patched, but your application code is safe only if it handles user input securely. Review how your code passes data to IMAP, POP3, or HTTP header functions.

Q: What is the difference between CVE-2026-0672 and CVE-2026-0865?

A: Both are header injection flaws. specifically targets the http.cookies module, while targets the WSGI header handling (wsgiref). They affect different parts of the web stack.

Q: Will this update break my existing Python 3.13 applications?

A: This is a patch release focusing on security fixes. It is intended to be backward compatible with the 3.13 series. However, it is best practice to test the update in a staging environment first.

Conclusion: Fortify Your Fedora 42 Python Environment Now

The disclosure of these 7 critical vulnerabilities in Python 3.13 represents a significant security inflection point for Fedora 42 administrators. From HTTP response splitting to mail server command injection, the attack surface is broad and the potential for damage is high.

Your next step is clear:

Execute the dnf upgrade command provided above immediately. After patching, conduct a brief audit of your applications for the specific injection patterns discussed. Subscribe to the Linux Security feed for real-time alerts on critical infrastructure threats.