🛡️ CVE-2026-50128 — mastodon

🟡 CVSS 5.3 — Medium ✅ No Known Exploit NVD
5.3
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Mastodon: Spoofing of attribution domains

Mastodon is a free, open-source social network server based on ActivityPub. From 4.3.0 until 4.5.11 and 4.4.18, Mastodon has a feature to let websites credit authors of their articles. To prevent false attribution claims, Mastodon uses the attributionDomains JSON-LD term, however, an error in how it is defined makes Linked Data Signatures on the toot:attributionDomains property ineffective. An attacker can arbitrarily modify the attributionDomains value of a legitimately signed Update activity and bypass Mastodon’s signature verification. This vulnerability is fixed in 4.5.11 and 4.4.18.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity low, availability none.

Affected software

CVE-2026-50128 is recorded against 2 packages.

  • mastodon
  • unknown

Timeline and source

Published on 6 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
github.com (Web)
nvd.nist.gov (Web)

Details

Severity MEDIUM
CVSS Score 5.3
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2026-07-06
Updated 2026-08-12
Modified 2026-07-06
Fix URL N/A

Affected Packages

Software From version Fixed in
mastodon — —
unknown — —

Similar Threats

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