Skip to main content
Public proof of concept

CVE-2021-26918

A public proof of concept exists; no exploitation attested.

  • Published2021-02-09
  • WeaknessCWE-434

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC
  1. 2021-02-0903:15CVE publishedNVD

Versions per branch

NVD · CISA-ADP
Probot bot
BranchAffectedFixed in
2021.x≤ 2021-02-08no fix published
2021.x= 2021-02-08no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-02-09
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-ghmj-xphc-2mq4

Frequently asked questions

What is CVE-2021-26918?

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.

Is CVE-2021-26918 actively exploited?

A proof-of-concept exploit exists for CVE-2021-26918, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2021-26918?

CVE-2021-26918 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Hear about the next vulnerability in your software

Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».

Get alerts for this productCISA KEV additions, November 2026Search CVEs

No credit card required · No monthly cap on website lookups · 250 API requests/month

Go further

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database

Sources for this record