CVE-2026-50128

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 97% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
5.3
EG Score
5.3(medium)
EPSS
2.9%
KEV
Not listed

Published

June 24, 2026

Last Modified

June 25, 2026

Advisory Details (1)

Auto-updated Jun 24, 2026
Patch available. Sources: github.
github Patch Available

Spoofing of attribution domains · Advisory · mastodon/mastodon · GitHub

https://github.com/mastodon/mastodon/security/advisories/GHSA-rwcw-vq68-g34p

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 16× in last 7d / 36× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-11 08:27 UTCEPSS rescore
  2. 2026-07-11 08:27 UTCEPSS rescore
  3. 2026-07-10 23:14 UTCEG score recompute
  4. 2026-07-09 21:34 UTCEG score recompute
  5. 2026-07-09 19:10 UTCEPSS rescore
  6. 2026-07-09 19:10 UTCEPSS rescore
  7. 2026-07-08 19:55 UTCEG score recompute
  8. 2026-07-08 15:16 UTCEPSS rescore
  9. 2026-07-08 15:16 UTCEPSS rescore
  10. 2026-07-07 18:14 UTCEG score recompute
  11. 2026-07-07 13:46 UTCEPSS rescore
  12. 2026-07-06 16:30 UTCEG score recompute
  13. 2026-07-06 16:27 UTCEPSS rescore
  14. 2026-07-06 02:23 UTCEPSS rescore
  15. 2026-07-05 14:45 UTCEG score recompute
  16. 2026-07-05 02:30 UTCEPSS rescore
  17. 2026-07-04 13:04 UTCEG score recompute
  18. 2026-07-03 11:25 UTCEG score recompute
  19. 2026-07-02 09:36 UTCEG score recompute
  20. 2026-07-01 15:07 UTCEPSS rescore
  21. 2026-07-01 07:58 UTCEG score recompute
  22. 2026-06-30 23:22 UTCEPSS rescore
  23. 2026-06-30 06:19 UTCEG score recompute
  24. 2026-06-29 14:06 UTCEPSS rescore
  25. 2026-06-29 14:06 UTCEPSS rescore
Show 11 more
  1. 2026-06-29 04:40 UTCEG score recompute
  2. 2026-06-28 14:07 UTCEPSS rescore
  3. 2026-06-28 04:56 UTCEPSS rescore
  4. 2026-06-28 04:56 UTCEPSS rescore
  5. 2026-06-28 03:01 UTCEG score recompute
  6. 2026-06-27 03:08 UTCEPSS rescore
  7. 2026-06-27 01:22 UTCEG score recompute
  8. 2026-06-25 23:42 UTCEG score recompute
  9. 2026-06-25 13:49 UTCEPSS rescore
  10. 2026-06-24 22:03 UTCEG score recompute
  11. 2026-06-24 22:03 UTCNVD updatefirst tracked

Frequently asked(5)

What is CVE-2026-50128?
CVE-2026-50128 is a medium vulnerability published on June 24, 2026. 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…
When was CVE-2026-50128 disclosed?
CVE-2026-50128 was first published in the National Vulnerability Database on June 24, 2026, with the most recent update on June 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-50128 actively exploited?
CVE-2026-50128 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 2.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-50128?
CVE-2026-50128 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-50128?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-50128, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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