CVE-2026-22245Network attack vector

Private service access via incomplete IP range blocklist

Published Jan 8, 2026 · Updated Jan 8, 2026

SSRF in Mastodon's outbound request filtering allows remote authenticated users to access loopback and local network services. PrivateAddressCheck compares destinations with IPv4 ranges but omits their IPv4-mapped IPv6 representations, allowing equivalent addresses through. Reachability requires control of a URL that the server fetches; successful requests can interact with otherwise private resources, while ALLOWED_PRIVATE_ADDRESSES intentionally exempts configured destinations.

CVSS severity7.1
High
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSRF in Mastodon's outbound request filtering allows remote authenticated users to access loopback and local network services. PrivateAddressCheck compares destinations with IPv4 ranges but omits their IPv4-mapped IPv6 representations, allowing equivalent addresses through. Reachability requires control of a URL that the server fetches; successful requests can interact with otherwise private resources, while ALLOWED_PRIVATE_ADDRESSES intentionally exempts configured destinations.

The record

CVE
CVE-2026-22245
Published
Jan 8, 2026
Updated
Jan 8, 2026
Vendor
Mastodon
Product
Mastodon
Classifications
CWE-918, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.2.29
  2. Affected versionversion=>= 4.3.0-beta.1, < 4.3.17
  3. Affected versionversion=>= 4.4.0-beta.1, < 4.4.11
  4. Affected versionversion=>= 4.5.0-beta.1, < 4.5.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mastodon · Mastodonversion=< 4.2.29; version=>= 4.3.0-beta.1, < 4.3.17; version=>= 4.4.0-beta.1, < 4.4.11; version=>= 4.5.0-beta.1, < 4.5.4

Published CVSS scores

7.1GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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