Vulnerability-Lookup

CVE-2026-22028 (GCVE-0-2026-22028)

Vulnerability from cvelistv5 – Published: 2026-01-08 14:16 – Updated: 2026-01-08 15:55

Title

Preact has JSON VNode Injection issue

Summary

Preact, a lightweight web development framework, JSON serialization protection to prevent Virtual DOM elements from being constructed from arbitrary JSON. A regression introduced in Preact 10.26.5 caused this protection to be softened. In applications where values from JSON payloads are assumed to be strings and passed unmodified to Preact as children, a specially-crafted JSON payload could be constructed that would be incorrectly treated as a valid VNode. When this chain of failures occurs it can result in HTML injection, which can allow arbitrary script execution if not mitigated by CSP or other means. Applications using affected Preact versions are vulnerable if they meet all of the following conditions: first, pass unmodified, unsanitized values from user-modifiable data sources (APIs, databases, local storage, etc.) directly into the render tree; second assume these values are strings but the data source could return actual JavaScript objects instead of JSON strings; and third, the data source either fails to perform type sanitization AND blindly stores/returns raw objects interchangeably with strings, OR is compromised (e.g., poisoned local storage, filesystem, or database). Versions 10.26.10, 10.27.3, and 10.28.2 patch the issue. The patch versions restore the previous strict equality checks that prevent JSON-parsed objects from being treated as valid VNodes. Other mitigations are available for those who cannot immediately upgrade. Validate input types, cast or validate network data, sanitize external data, and use Content Security Policy (CSP).

Severity ?

7.2 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U

CWE

CWE-843 - Access of Resource Using Incompatible Type ('Type Confusion')

Assigner

GitHub_M

References

URL

Tags

https://github.com/preactjs/preact/security/advis…

x_refsource_CONFIRM

Impacted products

	Vendor	Product	Version
	preactjs	preact	Affected: >= 10.26.5, < 10.26.10 Affected: >= 10.27.0, < 10.27.3 Affected: >= 10.28.0, < 10.28.2

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JSON

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GHSA-36HM-QXXP-PG3M

Vulnerability from github – Published: 2026-01-07 19:28 – Updated: 2026-01-08 21:19

Summary

Preact has JSON VNode Injection issue

Details

Impact

Vulnerability Type: HTML Injection via JSON Type Confusion

Affected Versions: Preact 10.26.5 through 10.28.1

Severity: Low to Medium (see below)

Who is Impacted?

Applications using affected Preact versions are vulnerable if they meet all of the following conditions:

Pass unmodified, unsanitized values from user-modifiable data sources (APIs, databases, local storage, etc.) directly into the render tree
Assume these values are strings but the data source could return actual JavaScript objects instead of JSON strings
The data source either:
Fails to perform type sanitization AND blindly stores/returns raw objects interchangeably with strings, OR
Is compromised (e.g., poisoned local storage, filesystem, or database)

Technical Details

Preact includes JSON serialization protection to prevent Virtual DOM elements from being constructed from arbitrary JSON. A regression introduced in Preact 10.26.5 caused this protection to be softened. In applications where values from JSON payloads are assumed to be strings and passed unmodified to Preact as children, a specially-crafted JSON payload could be constructed that would be incorrectly treated as a valid VNode. When this chain of failures occurs it can result in HTML injection, which can allow arbitrary script execution if not mitigated by CSP or other means.

Important Notes: - This regression was never present in preact-render-to-string - This is primarily an "expanded attack surface" issue rather than a standalone vulnerability - Exploitation requires either insecure API design (no type validation) or a compromised data source

Patches

Patched Versions: - 10.26.10 (for 10.26.x users) - 10.27.3 (for 10.27.x users) - 10.28.2 (for 10.28.x users)

Users should upgrade to the latest patch version of whatever minor version they are on, which can be done via npm update preact or by installing one of the above versions directly.

The patch versions simply restore the previous strict equality checks that prevent JSON-parsed objects from being treated as valid VNodes.

Mitigations

If you cannot upgrade immediately, implement the following mitigations:

Validate input types: Don't accept arbitrary objects as inputs in your API and blindly store them. Enforce strict type contracts at API boundaries.
Cast or validate network data: Don't assume strings are strings if your code got them from the network. Always cast to the expected type or validate before rendering.
Sanitize external data: Validate that data from external sources (APIs, storage, databases) matches expected types before passing it to preact.
Use Content Security Policy (CSP): Implement a strict CSP to prevent inline script execution as a defense-in-depth measure.

References

Reporter: YoungGeun Choi
Affected Versions: 10.26.5 - 10.28.1
Patched Versions: 10.26.10, 10.27.3, 10.28.2

Credits

Preact thanks YoungGeun Choi (Xvezda) for the responsible disclosure of this vulnerability and for providing detailed reproduction steps and proof-of-concept demonstrations.

Timeline

2026-01-04: Initial vulnerability report received
2026-01-05: Clarification requested regarding network/serialization boundary
2026-01-06: Network PoC provided demonstrating real-world exploitatibility
2026-01-06: Hotfix patches released (10.26.10, 10.27.3, 10.28.2)

Recommendation: All users of Preact 10.26.5 through 10.28.1 should upgrade to the appropriate patched version (10.26.10, 10.27.3, or 10.28.2) as soon as possible, and review their applications for proper input validation and sanitization practices.

Severity ?

7.2 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "preact"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "10.26.5"
            },
            {
              "fixed": "10.26.10"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "preact"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "10.27.0"
            },
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              "fixed": "10.27.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
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    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "preact"
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        {
          "events": [
            {
              "introduced": "10.28.0"
            },
            {
              "fixed": "10.28.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-22028"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-843"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-07T19:28:15Z",
    "nvd_published_at": "2026-01-08T15:15:44Z",
    "severity": "HIGH"
  },
  "details": "## Impact\n\n**Vulnerability Type:** HTML Injection via JSON Type Confusion\n\n**Affected Versions:** Preact 10.26.5 through 10.28.1\n\n**Severity:** Low to Medium (see below)\n\n### Who is Impacted?\n\nApplications using affected Preact versions are vulnerable if they meet **all** of the following conditions:\n\n1. **Pass unmodified, unsanitized values** from user-modifiable data sources (APIs, databases, local storage, etc.) directly into the render tree\n2. **Assume these values are strings** but the data source could return actual JavaScript objects instead of JSON strings\n3. The data source either:\n   - Fails to perform type sanitization **AND** blindly stores/returns raw objects interchangeably with strings, OR\n   - Is compromised (e.g., poisoned local storage, filesystem, or database)\n\n### Technical Details\n\nPreact includes JSON serialization protection to prevent Virtual DOM elements from being constructed from arbitrary JSON. A regression introduced in Preact 10.26.5 caused this protection to be softened. In applications where values from JSON payloads are assumed to be strings and passed unmodified to Preact as children, a specially-crafted JSON payload could be constructed that would be incorrectly treated as a valid VNode. When this chain of failures occurs it can result in HTML injection, which can allow arbitrary script execution if not mitigated by CSP or other means.\n\n**Important Notes:**\n- This regression was never present in `preact-render-to-string`\n- This is primarily an \"expanded attack surface\" issue rather than a standalone vulnerability\n- Exploitation requires either insecure API design (no type validation) or a compromised data source\n\n## Patches\n\n**Patched Versions:**\n- **10.26.10** (for 10.26.x users)\n- **10.27.3** (for 10.27.x users)\n- **10.28.2** (for 10.28.x users)\n\nUsers should upgrade to the latest patch version of whatever minor version they are on, which can be done via `npm update preact` or by installing one of the above versions directly.\n\nThe patch versions simply restore the previous strict equality checks that prevent JSON-parsed objects from being treated as valid VNodes.\n\n## Mitigations\n\nIf you cannot upgrade immediately, implement the following mitigations:\n\n- **Validate input types:** Don\u0027t accept arbitrary objects as inputs in your API and blindly store them. Enforce strict type contracts at API boundaries.\n- **Cast or validate network data:** Don\u0027t assume strings are strings if your code got them from the network. Always cast to the expected type or validate before rendering.\n- **Sanitize external data:** Validate that data from external sources (APIs, storage, databases) matches expected types before passing it to preact.\n- **Use Content Security Policy (CSP):** Implement a strict CSP to prevent inline script execution as a defense-in-depth measure.\n\n## References\n\n- **Reporter:** [YoungGeun Choi](https://github.com/Xvezda)\n- **Affected Versions:** 10.26.5 - 10.28.1\n- **Patched Versions:** 10.26.10, 10.27.3, 10.28.2\n\n## Credits\n\nPreact thanks **YoungGeun Choi (Xvezda)** for the responsible disclosure of this vulnerability and for providing detailed reproduction steps and proof-of-concept demonstrations.\n\n## Timeline\n\n- **2026-01-04:** Initial vulnerability report received\n- **2026-01-05:** Clarification requested regarding network/serialization boundary\n- **2026-01-06:** Network PoC provided demonstrating real-world exploitatibility\n- **2026-01-06:** Hotfix patches released (10.26.10, 10.27.3, 10.28.2)\n\n---\n\n**Recommendation:** All users of Preact 10.26.5 through 10.28.1 should upgrade to the appropriate patched version (10.26.10, 10.27.3, or 10.28.2) as soon as possible, and review their applications for proper input validation and sanitization practices.",
  "id": "GHSA-36hm-qxxp-pg3m",
  "modified": "2026-01-08T21:19:13Z",
  "published": "2026-01-07T19:28:15Z",
  "references": [
    {
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      "url": "https://github.com/preactjs/preact/security/advisories/GHSA-36hm-qxxp-pg3m"
    },
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      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-22028"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/preactjs/preact"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Preact has JSON VNode Injection issue"
}

FKIE_CVE-2026-22028

Vulnerability from fkie_nvd - Published: 2026-01-08 15:15 - Updated: 2026-01-08 18:08

Severity ?

7.2 (High) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/preactjs/preact/security/advisories/GHSA-36hm-qxxp-pg3m
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/preactjs/preact/security/advisories/GHSA-36hm-qxxp-pg3m

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Preact, a lightweight web development framework, JSON serialization protection to prevent Virtual DOM elements from being constructed from arbitrary JSON. A regression introduced in Preact 10.26.5 caused this protection to be softened. In applications where values from JSON payloads are assumed to be strings and passed unmodified to Preact as children, a specially-crafted JSON payload could be constructed that would be incorrectly treated as a valid VNode. When this chain of failures occurs it can result in HTML injection, which can allow arbitrary script execution if not mitigated by CSP or other means. Applications using affected Preact versions are vulnerable if they meet all of the following conditions: first, pass unmodified, unsanitized values from user-modifiable data sources (APIs, databases, local storage, etc.) directly into the render tree; second assume these values are strings but the data source could return actual JavaScript objects instead of JSON strings; and third, the data source either fails to perform type sanitization AND blindly stores/returns raw objects interchangeably with strings, OR is compromised (e.g., poisoned local storage, filesystem, or database). Versions 10.26.10, 10.27.3, and 10.28.2 patch the issue. The patch versions restore the previous strict equality checks that prevent JSON-parsed objects from being treated as valid VNodes. Other mitigations are available for those who cannot immediately upgrade. Validate input types, cast or validate network data, sanitize external data, and use Content Security Policy (CSP)."
    }
  ],
  "id": "CVE-2026-22028",
  "lastModified": "2026-01-08T18:08:18.457",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 7.2,
          "baseSeverity": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "UNREPORTED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "HIGH",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-01-08T15:15:44.853",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/preactjs/preact/security/advisories/GHSA-36hm-qxxp-pg3m"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/preactjs/preact/security/advisories/GHSA-36hm-qxxp-pg3m"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-843"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-22028 (GCVE-0-2026-22028)

GHSA-36HM-QXXP-PG3M

Impact

Who is Impacted?

Technical Details

Patches

Mitigations

References

Credits

Timeline

FKIE_CVE-2026-22028

Tags

Sightings

Nomenclature