CVE-2021-26918

9.8 CRITICAL 3% exploit odds No fix listed Code execution

What it is

The ProBot bot through 2021-02-08 for Discord might allow attackers to interfere with the intended purpose of the "Send an image when a user joins the server" feature (or possibly have unspecified other impact) because the uploader web service allows double extensions (such as .html.jpg) with the text/html content type. NOTE: there may not be cases in which an uploader web service is customer controlled; however, the nature of the issue has substantial interaction with customer controlled configuration. NOTE: the vendor states "This is just an uploader (like any other one) which uploads files to cloud storage and accepts various file types. There is no kind of vulnerability and it won't compromise either the client side or the server side.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.
Exploit odds: 2.6% chance of exploitation in the next 30 days (EPSS).
Fix: No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

2021-02-09 00:00 UTC ReservedThe CVE id was reserved by its CNA
2021-02-09 03:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 03:44 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 2.6% in the next 30 days (EPSS).
Severity: 9.8 CRITICAL (CVSS).
Fix: none linked yet, which raises it.

Details

Published: 2021-02-09 03:15 UTC
Last modified: 2026-06-17 03:44 UTC
Exploit probability: 2.6% · EPSS, next 30 days
Weakness: CWE-434 · Unrestricted file upload
Record status: Modified

Affected

Probot Bot ≤ 2021-02-08

Attack profile CVSS 3.1 · 9.8

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-26918.md and follow it. Check whether this project is affected by CVE-2021-26918. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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References

NVD record · CVE.org record