# What is CVE-2023-45803?

> CVE-2023-45803 is a medium-severity flaw (CVSS 4.2) in Urllib3 from Python, published on 17 October 2023. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 0.5%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.edgeprotect.io/what-is/cve-2023-45803

## At a glance

- **Verdict:** Plan it in. No sign of exploitation and a low forecast. Patch it in your normal update cycle.
- **EdgeProtect risk score:** 12 out of 100 (Info); action: Track. Kept up to date as the evidence changes.
- **Severity:** Medium (CVSS 4.2 out of 10)
- **Known to be exploited:** No, not on the list of flaws known to be exploited today
- **Chance of use in the next 30 days:** 0.5% (latest exploit-likelihood forecast)
- **Published:** 17 October 2023
- **Record last updated:** 3 November 2025
- **Main product:** Urllib3 from Python
- **Affected products:** 2

## What is CVE-2023-45803? In plain terms

An attacker has to be on the same local network with an administrator account, and nobody has to click anything. If it works, the attacker can read data.

### The official description

urllib3 is a user-friendly HTTP client library for Python. urllib3 previously wouldn't remove the HTTP request body when an HTTP redirect response using status 301, 302, or 303 after the request had its method changed from one that could accept a request body (like `POST`) to `GET` as is required by HTTP RFCs. Although this behavior is not specified in the section for redirects, it can be inferred by piecing together information from different sections and we have observed the behavior in other major HTTP client implementations like curl and web browsers. Because the vulnerability requires a previously trusted service to become compromised in order to have an impact on confidentiality we believe the exploitability of this vulnerability is low. Additionally, many users aren't putting sensitive data in HTTP request bodies, if this is the case then this vulnerability isn't exploitable. Both of the following conditions must be true to be affected by this vulnerability: 1. Using urllib3 and submitting sensitive information in the HTTP request body (such as form data or JSON) and 2. The origin service is compromised and starts redirecting using 301, 302, or 303 to a malicious peer or the redirected-to service becomes compromised. This issue has been addressed in versions 1.26.18 and 2.0.7 and users are advised to update to resolve this issue. Users unable to update should disable redirects for services that aren't expecting to respond with redirects with `redirects=False` and disable automatic redirects with `redirects=False` and handle 301, 302, and 303 redirects manually by stripping the HTTP request body.

### What kind of flaw is it?

- CWE-200: Exposure of Sensitive Information to an Unauthorized Actor

### How an attack on it works

- Where an attacker can be: On the same local network
- How hard it is to pull off: Hard: conditions must line up
- Login needed first: An administrator account
- Does someone have to click: No, nobody has to do anything
- What an attacker gets: Can read data

Severity vector: `CVSS:3.1/AV:A/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N`

## Is CVE-2023-45803 being exploited? Not that we know of

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 0.5%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 0.5%, 0.5%, 0.5%, 0.5%, 0.5%, 0.5%, 0.5%.

### Timeline

- 17 October 2023: Published
- 3 November 2025: Record last updated

### How EdgeProtect ranks it

CVE-2023-45803 scores **12 out of 100 (Info)**, with the action "Track".

Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less:

- Evidence it is being exploited: biggest factor
- How severe it is: strong factor
- How widely exposed it is: key context
- Real threat activity around it: key context

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it.

## Who is affected by CVE-2023-45803?

The published record lists 2 products. Versions are as published: "before 1.26.18" means every version up to, but not including, 1.26.18.

- [Urllib3](https://www.edgeprotect.io/product/python/urllib3) by [Python](https://www.edgeprotect.io/vendors/python) (Application): before 1.26.18, 2.0.0 to before 2.0.7
- [Fedora](https://www.edgeprotect.io/product/fedoraproject/fedora) by [Fedoraproject](https://www.edgeprotect.io/vendors/fedoraproject) (Operating system): 38

## How do I fix CVE-2023-45803?

1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? EdgeProtect can work it out from your public website, or you can pick it from a list.
2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisory first in the list.
3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood.

### References

- [github.com](https://github.com/urllib3/urllib3/commit/4e98d57809dacab1cbe625fddeec1a290c478ea9) (Patch)
- [github.com](https://github.com/urllib3/urllib3/security/advisories/GHSA-g4mx-q9vg-27p4) (Third-party advisory)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4R2Y5XK3WALSR3FNAGN7JBYV2B343ZKB/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/5F5CUBAN5XMEBVBZPHFITBLMJV5FIJJ5/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PPDPLM6UUMN55ESPQWJFLLIZY4ZKCNRX/) (Mailing list)
- [rfc-editor.org](https://www.rfc-editor.org/rfc/rfc9110.html#name-get) (Third-party advisory)
- [lists.debian.org](https://lists.debian.org/debian-lts-announce/2024/12/msg00020.html)

## Questions

### What is CVE-2023-45803?

CVE-2023-45803 is a medium-severity flaw in Urllib3 from Python, published on 17 October 2023. An attacker has to be on the same local network with an administrator account, and nobody has to click anything. If it works, the attacker can read data.

### How serious is CVE-2023-45803?

It scores 4.2 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2023-45803 is 12 out of 100, which is Info. Its action is "Track". No sign of exploitation and a low forecast. Patch it in your normal update cycle.

### Is CVE-2023-45803 being exploited?

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 0.5%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2023-45803 affect?

For Urllib3 from Python: before 1.26.18, 2.0.0 to before 2.0.7. The record lists 2 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2023-45803?

Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet.

## Does CVE-2023-45803 affect you?

EdgeProtect keeps checking for you:

- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
- **We match it to every flaw.** Over 400,000 published flaws, checked against your list.
- **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it.
- **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools.

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