SB2026042389 - Multiple vulnerabilities in Mastodon

Description

This security bulletin contains information about 2 vulnerabilities.

1) Improper Authorization (CVE-ID: CVE-2026-33869)

CWE-ID: CWE-285 - Improper Authorization

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to prevent a quote from being correctly processed on the server.

The vulnerability exists due to improper authorization handling in quote authorization when processing a quote before it has reached a server. A remote attacker can know of a quote in advance to prevent a quote from being correctly processed on the server.

2) Open redirect (CVE-ID: CVE-2026-33868)

CWE-ID: CWE-601 - URL Redirection to Untrusted Site ('Open Redirect')

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear

The vulnerability allows a remote attacker to redirect users to an arbitrary external site.

The vulnerability exists due to url redirection to an untrusted site in the /web/* route when handling specially encoded path segments. A remote attacker can send a specially crafted URL to redirect users to an arbitrary external site.

User interaction is required to follow the crafted link, and the issue involves URL-encoded slashes being interpreted as host-relative redirects.

Remediation

Install update from vendor's website.

References

• https://github.com/mastodon/mastodon/security/advisories/GHSA-q4g8-82c5-9h33
• https://github.com/advisories/GHSA-q4g8-82c5-9h33
• https://github.com/mastodon/mastodon/security/advisories/GHSA-xqw8-4j56-5hj6