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CVE-2026-45797 heyform CVE debrief

CVE-2026-45797 is a stored cross-site scripting (XSS) vulnerability in HeyForm, an open-source form builder. The vulnerability exists in the `/api/upload` endpoint, which allows unauthenticated file uploads, including SVG files. These uploaded SVGs are stored in the static assets directory and served with `Content-Type: image/svg+xml` by Express's serve-static middleware. This allows an attacker to achieve stored cross-site scripting (XSS) on the heyform domain without any authentication. The issue was patched in version 3.0.0-rc.7. Users of HeyForm should ensure they are running version 3.0.0-rc.7 or later to mitigate the risk.

Vendor
heyform
Product
Unknown
CVSS
MEDIUM 6.4
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-20
Original CVE updated
2026-07-22
Advisory published
2026-07-20
Advisory updated
2026-07-22

Who should care

Users of HeyForm, especially those hosting it on their own servers, should be aware of this vulnerability and ensure they are running version 3.0.0-rc.7 or later to mitigate the risk. This includes operators, platform administrators, vulnerability management teams, and security teams who need to assess the impact of this vulnerability on their deployments.

Technical summary

The `/api/upload` endpoint in HeyForm allows unauthenticated file uploads, including SVG files. These SVG files are stored in the static assets directory and served with `Content-Type: image/svg+xml`. An attacker can exploit this by uploading a malicious SVG file that contains JavaScript code, which can then be executed by other users who access the file. This is a stored XSS vulnerability because the malicious code is stored on the server and executed when a user accesses the file. The vulnerability was patched in version 3.0.0-rc.7.

Defensive priority

Medium

Recommended defensive actions

  • Update HeyForm to version 3.0.0-rc.7 or later
  • Restrict access to the `/api/upload` endpoint to authenticated users only
  • Validate and sanitize all uploaded files, especially SVG files
  • Use a web application firewall (WAF) to detect and prevent XSS attacks
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record was published on 2026-07-20T16:17:00.743Z and last modified on 2026-07-20T19:17:23.003Z. The NVD entry is currently in the 'Received' status. The vulnerability was patched in version 3.0.0-rc.7 of HeyForm. There are no known exploit details or reports of this vulnerability being used in attacks. However, defenders should verify that their deployments are updated to the patched version to prevent potential attacks.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-45797 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-45797

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

  • CVE-2026-45797 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-45797

    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.