CVE-2015-2296

What it actually does

The resolve_redirects function in requests sessions.py permits a redirect response to inject a cookie lacking a host value, allowing the attacker-supplied session identifier to be accepted and reused across domains.

Why it matters to the business

Organizations still running unpatched versions of the requests library face risk of session takeover, resulting in unauthorized access to user accounts and potential data exposure; the vulnerability is more than a decade old with no known active exploitation campaigns.

How an attack unfolds

An attacker crafts a redirect that returns a Set-Cookie header without a domain attribute, causes the victim application to follow the redirect using the vulnerable requests library, and thereby forces the victim's browser or client to adopt the attacker's session identifier for subsequent requests.

How to fix it

Upgrade the Python requests package to a version newer than 2.5.3 on all affected systems including Mageia and Ubuntu; verify the installed version with pip show requests and replace any direct or transitive dependency on the vulnerable range.

How to confirm the fix worked

Inventory all Python environments for requests versions 2.1.0-2.5.3, confirm upgrade via package manager output, and re-test redirect handling in applications that use sessions.py to ensure cookies now carry proper host attributes.

Typical attack path

1. Attacker prepares a malicious redirect endpoint returning a cookie without host restriction
2. Victim application issues a request that follows the redirect via the vulnerable requests library
3. The injected cookie is stored and reused in the established session
4. Attacker uses the fixed session identifier to impersonate the victim

How to detect it

Examine application and proxy logs for redirect responses containing Set-Cookie headers that lack domain or host attributes; correlate with subsequent requests using the same session identifier from unexpected sources.

What your security team should do

• Immediately scan codebases and container images for the vulnerable requests versions and prioritize upgrades
• Add package version checks to CI/CD pipelines to block future inclusion of requests <= 2.5.3
• Review session management code that follows redirects and enforce strict cookie domain validation as a defense-in-depth measure