Vulnerability in mastodon (CVE-2026-50128)
Summary
Vulnerability in mastodon (CVE-2026-50128). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 4.5.11 or later.
Original description
The description as published by the source.
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.
Source: NIST National Vulnerability Database NVD
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-50128 has been found in mastodon.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade mastodon to 4.5.11 or later.
If unsure, ask your IT team or search "mastodon CVE-2026-50128" on the vendor's site.
CVE-2026-50128 (mastodon) — CWE-354 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 4.5.11 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-354) exists in mastodon.
Check the vendor advisory for the affected versions of mastodon.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to 4.5.11.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'mastodon' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'mastodon' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
mastodonを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade mastodon to 4.5.11ステージング環境で 4.5.11 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- web github.com
- web github.com
- web nvd.nist.gov