CyberSecBulletin
CVE-2026-42462NVD status: Deferred

fedify: Incorrect Behavior Order: Validate Before Canonicalize

Published Updated By the CyberSecBulletin desk

CVE-2026-42462 is a high-severity incorrect behavior order: validate before canonicalize vulnerability in fedify from Fedify-dev, with a CVSS 3.1 base score of 7.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected fedify versions: >= 2.2.0, < 2.2.3; >= 2.1.0, < 2.1.14; >= 2.0.0, < 2.0.18, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.17% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of fedify you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on github.com for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Fedify-devfedify>= 2.2.0, < 2.2.3; >= 2.1.0, < 2.1.14; >= 2.0.0, < 2.0.18; >= 1.10.0, < 1.10.10; < 1.9.11Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
HighSuccess depends on conditions outside the attacker's control.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
LowSome restricted data can be read.
Integrity
HighData or code can be modified at will.
Availability
LowPerformance or availability is reduced.

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:L. Scored by CNA (github.com).

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Incorrect Behavior Order: Validate Before Canonicalize

The product validates input before it is canonicalized.

How developers prevent this class of flaw

  • Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.

More Incorrect Behavior Order: Validate Before Canonicalize vulnerabilities (CWE-180)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in fedify

All fedify vulnerabilities

Recent Incorrect Behavior Order: Validate Before Canonicalize vulnerabilities

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