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High, CVSS 7.0amended

Fedify has an LD-Signature Bypass via JSON-LD Named-Graph Restructuring

CVE-2026-42462GHSA-9rfg-v8g9-9367

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@fedify/fedify 2.2.3, 2.1.14, 2.0.18, 1.10.10, 1.9.11), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm @fedify/fedify

    Affected
    >= 2.2.0, < 2.2.3>= 2.1.0, < 2.1.14>= 2.0.0, < 2.0.18>= 1.10.0, < 1.10.10< 1.9.11
    Fixed in
    1.9.11, 2.0.18, 1.10.10, 2.2.3, 2.1.14

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.0 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:L
EPSS
  • CVE-2026-42462: 0.17% estimated exploitation activity in the next 30 days; percentile 6.48 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

As told on Discord earlier, multiple projects are affected, and we would like to coordinate. For now, we are aiming at a May 6th release date, but this is not set in stone yet. Summary 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. Details The vulnerability essentially boils down to the signature being on the canonical RDF graph representation of the JSON-LD document, and JSON-LD offering many ways to represent the same graph. One of the issues is that by taking a signed Activity with an embedded object, an attacker can move the top-level Activity to a @graph property and move the activity's object to the top-level. Such a transformation preserves the signature and changes how the payload is interpreted by pretty much all ActivityPub implementations, making them process the object and ignore the…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-9rfg-v8g9-9367

  2. Revision 1 · created ·

    Published from osv record GHSA-9rfg-v8g9-9367

Agent brief

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# Patch Next advisory brief: CVE-2026-42462

Advisory: Fedify has an LD-Signature Bypass via JSON-LD Named-Graph Restructuring
IDs: CVE-2026-42462, GHSA-9rfg-v8g9-9367
Record: https://patchnext.com/advisories/cve-2026-42462 (revision 2, source checked 26 Oct 2026, 12:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @fedify/fedify 2.2.3, 2.1.14, 2.0.18, 1.10.10, 1.9.11. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @fedify/fedify: affected >= 2.2.0, < 2.2.3; >= 2.1.0, < 2.1.14; >= 2.0.0, < 2.0.18; >= 1.10.0, < 1.10.10; < 1.9.11; fixed in 1.9.11, 2.0.18, 1.10.10, 2.2.3, 2.1.14

## Suggested inspection (read-only)
- `npm ls @fedify/fedify --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @fedify/fedify.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9rfg-v8g9-9367 (OSV record GHSA-9rfg-v8g9-9367 lists affected ranges: npm @fedify/fedify >=2.2.0 =2.1.0 =2.0.0 =1.10.0 =0 <1.9.11 (fixed))
- Verified: https://github.com/advisories/GHSA-9rfg-v8g9-9367 (GitHub-reviewed advisory GHSA-9rfg-v8g9-9367 lists affected ranges: npm @fedify/fedify >=2.2.0 =2.1.0 =2.0.0 =1.10.0 =0 <1.9.11)

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