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CVE-2026-22245

Mastodon has SSRF Protection bypass

HIGH
7.5
CVSS Score
Published: January 8, 2026 at 03:23 PM UTC
Updated: June 17, 2026 at 10:19 AM UTC
2 products affected across 2 vendorsMastodonMastodon

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Severity
HIGH7.5
Exploit prediction
EPSS 0.3%
SSVC
No known exploit

Description

Mastodon is a free, open-source social network server based on ActivityPub. By nature, Mastodon performs a lot of outbound requests to user-provided domains. Mastodon, however, has some protection mechanism to disallow requests to local IP addresses (unless specified in `ALLOWED_PRIVATE_ADDRESSES`) to avoid the "confused deputy" problem. The list of disallowed IP address ranges was lacking some IP address ranges that can be used to reach local IP addresses. An attacker can use an IP address in the affected ranges to make Mastodon perform HTTP requests against loopback or local network hosts, potentially allowing access to otherwise private resources and services. This is fixed in Mastodon v4.5.4, v4.4.11, v4.3.17 and v4.2.29.

Affected

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

Mastodon· Joinmastodon
95%
v < 4.2.294.3.0 ≤ v < 4.3.174.4.0 ≤ v < 4.4.114.5.0 ≤ v < 4.5.4
Mastodon· Mastodon
60%
v < 4.2.29v < 4.3.17v < 4.4.11v < 4.5.4
Affected range stops below 4.2.29, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.3.17, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.4.11, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.5.4, so it looks safe — our inference, not a vendor statement

References (4)

x_refsource_CONFIRMVendor Advisory
Source: cverecord
https://github.com/mastodon/mastodon/security/advisories/GHSA-xfrj-c749-jxxq
x_refsource_MISCPatch
Source: cverecord
https://github.com/mastodon/mastodon/commit/0f4e8a6240b5af1f2c3f34d2793d8610c6ef2aca
x_refsource_MISCPatch
Source: cverecord
https://github.com/mastodon/mastodon/commit/17022907866710a72a1b1fc0a5ce9538bad1b4c3
x_refsource_MISCPatch
Source: cverecord
https://github.com/mastodon/mastodon/commit/71ae4cf2cf5138ccdda64b1b1d665849b688686d

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

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

CVSS

7.5HIGH[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-918

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