What is CVE-2026-33868?

CVE-2026-33868 is a medium-severity vulnerability in Mastodon, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 4.3/10. Published 2026-03-27.

How severe is CVE-2026-33868?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Is CVE-2026-33868 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Open Redirect in Mastodon

CVE-2026-33868

Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.5.8, 4.4.15, and 4.3.21, an unauthenticated Open Redirect vulnerability (CWE-601) exists in the `/web/*` route due to improper handling of URL-…

Vulnerability class: Open Redirect

EPSS: 0.014 (80.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N.

Affected products

Mastodon — versions >= 4.5.0, < 4.5.8, >= 4.4.0, < 4.4.15, < 4.3.21

Weakness classification (CWE)

CWE-601 — URL Redirection to Untrusted Site (Open Redirect)

Public proof-of-concept exploits

O99099O/By-Poloss..-..CVE-2026-33868

References

https://github.com/mastodon/mastodon/security/advisories/GHSA-xqw8-4j56-5hj6 (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-33868?: CVE-2026-33868 is a medium-severity vulnerability in Mastodon, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 4.3/10. Published 2026-03-27.
How severe is CVE-2026-33868?: Medium severity. CVSS v3 base score is 4.3 out of 10.
Is CVE-2026-33868 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.