# CVE-2024-37891: Proxy-Authorization request header isn't stripped during cross-origin redirects in urllib3 > Attackers can steal Proxy-Authorization credentials if users manually set the header without using built-in proxy support during cross-origin redirects. - **Severity:** Medium 4.4 (`CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N`) - **Exploited in the wild:** Not known - **Login needed:** An administrator - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 17 Jun 2024 - **Updated:** 3 Nov 2025 - **Also known as:** ALSA-2024:4422, ALSA-2024:5309, ALSA-2024:6162, ALSA-2024:8842, ALSA-2024:8843, ALSA-2024:9457, ALSA-2024:9458, AZL-42703, AZL-42733, AZL-42769, AZL-59699, CLSA-2024-1729512774, CLSA-2024-1730142536, CLSA-2025-1763943168, CLSA-2026-1776904634, DEBIAN-CVE-2024-37891, ECHO-29eb-7008-1a39, GHSA-34jh-p97f-mpxf, MGASA-2024-0347, MINI-rgmv-pj75-fmrg, MINI-vhgg-32vv-g4w3, OESA-2024-1945, OESA-2024-1946, OESA-2024-1947, OESA-2024-2037, PYSEC-2026-1995, RHSA-2024:4422, RHSA-2024:4730, RHSA-2024:4744, RHSA-2024:4746, RHSA-2024:5041, RHSA-2024:5309, RHSA-2024:5526, RHSA-2024:5622, RHSA-2024:5627, RHSA-2024:5633, RHSA-2024:6162, RHSA-2024:6239, RHSA-2024:6240, RHSA-2024:6310, RHSA-2024:6358, RHSA-2024:8035, RHSA-2024:8842, RHSA-2024:8843, RHSA-2024:9457, RHSA-2024:9458, RHSA-2024:9922, RHSA-2024:9923, RHSA-2024:9985, RLSA-2024:5309, RLSA-2024:8842, RLSA-2024:8843, RLSA-2024:9457, ROOT-APP-PYPI-CVE-2024-37891, SUSE-SU-2024:2320-1, SUSE-SU-2024:2662-1, SUSE-SU-2024:2879-1, SUSE-SU-2024:4358-1, SUSE-SU-2025:20037-1, UBUNTU-CVE-2024-37891, USN-7084-1, USN-7084-2 ## What is CVE-2024-37891? CVE-2024-37891 is a medium-severity vulnerability in Debian Debian Linux, published on 17 Jun 2024. An attacker needs administrator access to exploit it, with no action from the victim. ### Official description urllib3 is a user-friendly HTTP client library for Python. When using urllib3's proxy support with `ProxyManager`, the `Proxy-Authorization` header is only sent to the configured proxy, as expected. However, when sending HTTP requests *without* using urllib3's proxy support, it's possible to accidentally configure the `Proxy-Authorization` header even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat the `Proxy-Authorization` HTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects. Because this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the `Proxy-Authorization` header during cross-origin redirects to avoid the small chance that users are doing this on accident. Users should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the `Proxy-Authorization` header, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach. We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited: 1. Setting the `Proxy-Authorization` header without using urllib3's built-in proxy support. 2. Not disabling HTTP redirects. 3. Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin. Users are advised to update to either version 1.26.19 or version 2.2.2. Users unable to upgrade may use the `Proxy-Authorization` header with urllib3's `ProxyManager`, disable HTTP redirects using `redirects=False` when sending requests, or not user the `Proxy-Authorization` header as mitigations. Weakness: CWE-669 (Incorrect Resource Transfer Between Spheres) ## Which versions are affected by CVE-2024-37891? 5 open source packages ship an affected version, including urllib3. It affects 3 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `urllib3` | PyPI | All versions | 1.26.19, 2.2.2 | | `urllib3` | PyPI | All versions | 1.26.19 | | `urllib3` | PyPI | All versions | 1.26.19 | | `urllib3` | PyPI | From 2.0.0 | 2.2.2 | | `urllib3` | PyPI | From 2.0.0 | 2.2.2 | | `python3-urllib3` | AlmaLinux:8 | All versions | 1.24.2-8.el8_10 | | `python3.11-urllib3` | AlmaLinux:8 | All versions | 1.26.12-4.el8_10 | | `python3.12-urllib3` | AlmaLinux:8 | All versions | 1.26.19-1.el8_10 | | `fence-agents-aliyun` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-all` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-amt-ws` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-apc` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-apc-snmp` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-aws` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-azure-arm` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-bladecenter` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-brocade` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-cisco-mds` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-cisco-ucs` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-common` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-compute` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-drac5` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-eaton-snmp` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-emerson` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-eps` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-gce` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-heuristics-ping` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-hpblade` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-ibm-powervs` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-ibm-vpc` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-ibmblade` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-ifmib` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-ilo-moonshot` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-ilo-mp` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-ilo-ssh` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-ilo2` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-intelmodular` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-ipdu` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-ipmilan` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | | `fence-agents-kdump` | AlmaLinux:9 | All versions | 4.10.0-62.el9_4.4.alma.1 | Products: Debian Debian Linux, Netapp Active Iq Unified Manager, Python Urllib3. ## How do I fix CVE-2024-37891? Upgrade urllib3 to a fixed version for your release line: 1.26.19 or 2.2.2. ## Is CVE-2024-37891 being exploited? There is no known exploitation of CVE-2024-37891 in the wild and no public exploit code. ## Other vulnerabilities in Debian Debian Linux - [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild) - [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild) - [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild) - [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild) - [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2024-37891 and fix it if it is affected. What it is: CVE-2024-37891 is a medium-severity vulnerability in Debian Debian Linux, published on 17 Jun 2024. An attacker needs administrator access to exploit it, with no action from the victim. Exploitation: There is no known exploitation of CVE-2024-37891 in the wild and no public exploit code. Affected packages and fixed versions: - urllib3 (PyPI): affected all versions; fixed in 1.26.19, 2.2.2 - urllib3 (PyPI): affected all versions; fixed in 1.26.19 - urllib3 (PyPI): affected all versions; fixed in 1.26.19 - urllib3 (PyPI): affected from 2.0.0; fixed in 2.2.2 - urllib3 (PyPI): affected from 2.0.0; fixed in 2.2.2 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2024-37891/ (Markdown: https://insights.sbomify.com/CVE-2024-37891/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2024-37891 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-37891 - OSV: https://osv.dev/vulnerability/CVE-2024-37891 --- From sbomify Insights: https://insights.sbomify.com/CVE-2024-37891/ Summaries are generated and may contain mistakes; the official description above is the record.