CVE-2021-26918: The ProBot bot through 2021-02-08 for Discord might allow attackers to interfere with the intended purpose of

Q: How do I fix CVE-2021-26918?

bot: upgrade to newer than 2021-02-08. Exact commands for each OS are on this page.

Q: Is CVE-2021-26918 being exploited?

CVE-2021-26918 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-26918 affect?

CVE-2021-26918 affects bot. Severity is critical (CVSS 9.8). 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 serv

Q: How urgent is CVE-2021-26918?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2021-26918 is a critical-severity flaw (CVSS 9.8) affecting bot. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 subst

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.6% (top 15%)
CISA exploited list	No
Weakness	CWE-434
Published	2021-02-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: probot

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-02-09 03:15 UTCPublished CVE record published
2026-06-17 03:44 UTCUpdated Record last modified

probot bot UPGRADE

Affected: <= 2021-02-08

Fixed in: newer than 2021-02-08

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy bot || rpm -q bot || bot --version

2. UPGRADE to newer than 2021-02-08 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade bot

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bot

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-26918?

bot: upgrade to newer than 2021-02-08. Exact commands for each OS are on this page.

Is CVE-2021-26918 being exploited?

CVE-2021-26918 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-26918 affect?

CVE-2021-26918 affects bot. Severity is critical (CVSS 9.8). 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 serv

How urgent is CVE-2021-26918?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Discord vulnerabilities

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References

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