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CVE-2026-42462 fedify-dev CVE debrief

CVE-2026-42462 is a HIGH severity vulnerability in Fedify, a TypeScript library for building federated server apps. Prior to versions 1.9.11, 1.10.10, 2.0.18, 2.1.14, and 2.2.3, an attacker can make use of JSON-LD features to restructure a JSON-LD document that would change how Fedify interprets it without changing its Linked Data Signature, allowing them to alter a third-party signed activity they have received. This vulnerability has a CVSS score of 7 and is considered HIGH severity. The vulnerability was published on [cvePublishedAt] and last modified on [cveModifiedAt].

Vendor
fedify-dev
Product
fedify
CVSS
HIGH 7
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-10
Original CVE updated
2026-06-11
Advisory published
2026-06-10
Advisory updated
2026-06-11

Who should care

Users of Fedify library versions prior to 1.9.11, 1.10.10, 2.0.18, 2.1.14, and 2.2.3 should be aware of this vulnerability and take steps to upgrade to a patched version.

Technical summary

The vulnerability allows an attacker to bypass JSON-LD signature verification by restructuring a JSON-LD document without changing its Linked Data Signature. This could allow an attacker to alter a third-party signed activity they have received.

Defensive priority

HIGH

Recommended defensive actions

  • Upgrade to Fedify library versions 1.9.11, 1.10.10, 2.0.18, 2.1.14, or 2.2.3 or later.
  • Review and update any third-party signed activities received to ensure they have not been altered.

Evidence notes

The CVE record [resourceLinkAnnotations:cve-org] and NVD detail [resourceLinkAnnotations:nvd] provide additional information about this vulnerability.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-42462 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-42462

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-42462 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-42462

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.