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TI-2026-17855 Aliases CVE-2026-22245

Mastodon has SSRF Protection bypass

Priority LOW 31CWE-918Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
—
Confidentiality · integrity · availability
None · High · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00289 21st percentileScored 2026-11-07
Fix Fixed mastodon (mastodon): 4.2.29, 4.3.17, 4.4.11 +1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
mastodonmastodonbefore 4.2.29; 4.3.0-beta.1 to before 4.3.17; 4.4.0-beta.1 to before 4.4.11; 4.5.0-beta.1 to before 4.5.44.2.29, 4.3.17, 4.4.11, 4.5.4Patch availableCNA
  • mastodon Vendormastodon Affected before 4.2.29; 4.3.0-beta.1 to before 4.3.17; 4.4.0-beta.1 to before 4.4.11; 4.5.0-beta.1 to before 4.5.4 Fixed in 4.2.29, 4.3.17, 4.4.11, 4.5.4 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*before 4.2.29; 4.3.0 to before 4.3.17; 4.4.0 to before 4.4.11; 4.5.0 to before 4.5.4Vulnerablemastodon
  • cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:* Versions before 4.2.29; 4.3.0 to before 4.3.17; 4.4.0 to before 4.4.11; 4.5.0 to before 4.5.4 Vulnerable ·mastodon

Remediation

  • Fix · CNA mastodon (mastodon) Fixed in 4.2.29, 4.3.17, 4.4.11, 4.5.4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-22245

References

Patch 3

Advisory 1

  • TI-2022-02004 Improper Restriction of Excessive Authentication Attempts in mastodon/mastodon CVSS 3.1CRITICAL 9.8
  • TI-2025-34613 Mastodon e‑mail throttle misconfiguration allows unlimited email confirmations against unconfirmed emails CVSS 3.1HIGH 7.5
  • TI-2022-22936 Mastodon through 4.0.2 allows attackers to cause a denial of service (large Sidekiq pull… CVSS 3.1HIGH 7.5
  • TI-2023-18301 Mastodon vulnerable to arbitrary file creation through media attachments CVSS 3.1CRITICAL 10.0
  • TI-2023-13359 Mastodon's blind LDAP injection in login allows the attacker to leak arbitrary attributes from LDAP database CVSS 3.1HIGH 7.7
  • TI-2024-16846 External OpenID Connect Account Takeover by E-Mail Change in mastodon CVSS 3.1HIGH 7.4
See all 41 →

Sources

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