# CVE-2026-118652: Echo: Reflected Cross-Site Scripting (XSS) via unsanitized JSONP callback in Context.JSONP / Context.JSONPBlob

Status: published. Published: 2026-10-28. Updated: 2026-11-03.

Echo is a Go web framework. Prior to 4.16.0 and 5.4.0, Context.JSONP and Context.JSONPBlob concatenate an unvalidated callback value into a JavaScript response. A route that passes attacker-controlled input as the callback can return executable script syntax, allowing reflected cross-site scripting when a user loads the crafted response. The vulnerable jsonPBlob path performs no callback validation or escaping, and exploitation requires an application route that exposes attacker control over the callback argument. This issue is fixed in 4.16.0 and 5.4.0.

## Remediation

- fix: github.com/labstack/echo/v5 (Go): OSV reports a fixed version 5.4.0. Check the advisory for supported release branches. (source: OSV GHSA-h9g5-28mm-hx3g) — https://github.com/advisories/GHSA-h9g5-28mm-hx3g
- fix: github.com/labstack/echo/v4 (Go): OSV reports a fixed version 4.16.0. Check the advisory for supported release branches. (source: OSV GHSA-h9g5-28mm-hx3g) — https://github.com/advisories/GHSA-h9g5-28mm-hx3g

## Affected products and versions

- labstack / echo: < 4.16.0 (affected); >= 5.0.0, < 5.4.0 (affected). Source: CNA: GitHub_M
-  / github.com/labstack/echo/v5 (github.com/labstack/echo/v5): ≥ 0; < 5.4.0 (affected, semver); OSV events: introduced 0; fixed 5.4.0. Source: OSV GHSA-h9g5-28mm-hx3g
-  / github.com/labstack/echo/v4 (github.com/labstack/echo/v4): ≥ 0; < 4.16.0 (affected, semver); OSV events: introduced 0; fixed 4.16.0. Source: OSV GHSA-h9g5-28mm-hx3g

## Severity and prioritization

- CVSS 3.1: 6.1 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: 0.24% as of 2026-11-02; percentile 15.04%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-79

## Exploit evidence

- exploit: https://github.com/labstack/echo/security/advisories/GHSA-h9g5-28mm-hx3g (ADP: CISA-ADP)

## References

- https://github.com/labstack/echo/security/advisories/GHSA-h9g5-28mm-hx3g (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/labstack/echo/commit/b838391e2eade87ae7e5a09d7bb5087bec271ec1 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/labstack/echo/commit/fc410094b2f3415cf2bf5204082137b205bfd5af (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/labstack/echo/releases/tag/v4.16.0 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/labstack/echo/releases/tag/v5.4.0 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/labstack/echo/security/advisories/GHSA-h9g5-28mm-hx3g (ADP: CISA-ADP; exploit)

- https://github.com/advisories/GHSA-h9g5-28mm-hx3g (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-h9g5-28mm-hx3g (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-118652; retrieved 2026-11-03; source updated 2026-11-03

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-h9g5-28mm-hx3g; retrieved 2026-11-03; source updated 2026-10-28

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-118652; retrieved 2026-11-03; source updated Not reported

Revision: 6c210fbc2aa92757d6204ef331a42fa4177f413b4bb2079a7a9df69fc56f2224

Canonical: https://y2.dev/cve/CVE-2026-118652

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