CVE-2026-72916
Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses
Description
Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1, PrivateAddressCheck.private_address? in app/lib/private_address_check.rb normalized IPv4-mapped IPv6 addresses but did not recognize IPv4-compatible IPv6 addresses with IPAddr#ipv4_compat?. An attacker could supply an address in the omitted range to bypass the ALLOWED_PRIVATE_ADDRESSES protection and make Mastodon send HTTP requests to loopback interfaces, potentially accessing private resources and services. Exploitation requires a system that supports the obsolete IPv4-compatible IPv6 mechanism. This issue is fixed in versions 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1.
INFO
Published Date :
Aug. 10, 2026, 10:17 p.m.
Last Modified :
Aug. 10, 2026, 10:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-72916
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update Mastodon to version 4.4.21 or later.
- Update Mastodon to version 4.5.14 or later.
- Update Mastodon to version 4.6.4 or later.
- Update Mastodon to version 4.7.0-beta.1 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-72916.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-72916 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-72916
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-72916 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-72916 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Aug. 10, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'mastodon', 'product': 'mastodon', 'versions': [{'status': 'affected', 'version': '< 4.4.21'}, {'status': 'affected', 'version': '>= 4.5.0-beta.1, < 4.5.14'}, {'status': 'affected', 'version': '>= 4.6.0-beta.1, < 4.6.4'}]}] Added Description Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1, PrivateAddressCheck.private_address? in app/lib/private_address_check.rb normalized IPv4-mapped IPv6 addresses but did not recognize IPv4-compatible IPv6 addresses with IPAddr#ipv4_compat?. An attacker could supply an address in the omitted range to bypass the ALLOWED_PRIVATE_ADDRESSES protection and make Mastodon send HTTP requests to loopback interfaces, potentially accessing private resources and services. Exploitation requires a system that supports the obsolete IPv4-compatible IPv6 mechanism. This issue is fixed in versions 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1. Added CVSS V4.0 AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-918 Added CWE CWE-1286 Added Reference https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892 Added Reference https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074 Added Reference https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b Added Reference https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d Added Reference https://github.com/mastodon/mastodon/releases/tag/v4.4.21 Added Reference https://github.com/mastodon/mastodon/releases/tag/v4.5.14 Added Reference https://github.com/mastodon/mastodon/releases/tag/v4.6.4 Added Reference https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1 Added Reference https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276