CVE-2026-42462
Received Received - Intake
JSON-LD Signature Bypass in Fedify

Publication date: 2026-06-10

Last updated on: 2026-06-10

Assigner: GitHub, Inc.

Description
Fedify is a TypeScript library for building federated server apps powered by ActivityPub. 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. Versions 1.9.11, 1.10.10, 2.0.18, 2.1.14, and 2.2.3 fix the issue.
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Meta Information
Published
2026-06-10
Last Modified
2026-06-10
Generated
2026-06-11
AI Q&A
2026-06-11
EPSS Evaluated
N/A
NVD
CVE-2026-42462
Affected Vendors & Products
Currently, no data is known.
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-347 The product does not verify, or incorrectly verifies, the cryptographic signature for data.
CWE-436 Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state.
CWE-180 The product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step.
CWE-1289 The product receives an input value that is used as a resource identifier or other type of reference, but it does not validate or incorrectly validates that the input is equivalent to a potentially-unsafe value.
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Impact Analysis

The vulnerability can allow an attacker to modify signed activities from third parties without invalidating their signatures. This could lead to unauthorized changes in data or actions within applications using the affected Fedify versions, potentially causing integrity issues, misinformation, or unauthorized operations.

Executive Summary

This vulnerability affects the Fedify TypeScript library used for building federated server applications powered by ActivityPub. Before certain fixed versions, an attacker could exploit JSON-LD features to restructure a JSON-LD document in a way that changes how Fedify interprets it without altering its Linked Data Signature. This manipulation allows the attacker to alter a third-party signed activity they have received.

Mitigation Strategies

To mitigate this vulnerability, you should upgrade Fedify to one of the fixed versions: 1.9.11, 1.10.10, 2.0.18, 2.1.14, or 2.2.3.

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