CVE-2026-46348

Mastodon: SSRF Bypass via IPv6 Unspecified Address (::)

HIGH

8.7

CVSS Score

Published: June 24, 2026 at 07:39 PM UTC

Updated: June 27, 2026 at 11:42 AM UTC

1 product affected across 1 vendorMastodon

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Severity

HIGH8.7

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

Description

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.10, 4.4.17, and 4.3.23, the list of disallowed IP address ranges was lacking an IP address range that can be used to reach local IP addresses. An attacker can use an IP address in the affected range to make Mastodon perform HTTP requests against loopback interfaces, potentially allowing access to otherwise private resources and services. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mastodon · Mastodon

60%

v < 4.5.10

Affected range stops below 4.5.10, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (1)

x_refsource_CONFIRM

Source: cverecord

https://github.com/mastodon/mastodon/security/advisories/GHSA-crr4-7rm4-8gpw

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.7HIGHGitHub_M

Vector?

Quick Info

StatusDEFERRED

CWE

CWE-918

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