Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Echo v5 before 5.4.0 and Echo v4 before 4.16.0 do not validate the callback parameter in Context.JSONP and Context.JSONPBlob, so a callback supplied by an attacker is written into the JavaScript response unchanged. An attacker can get a victim to open a crafted link, which can run arbitrary JavaScript in the victim's browser session on the affected site. Upgrade to github.com/labstack/echo/v5 5.4.0 or github.com/labstack/echo/v4 4.16.0; the fixed versions accept only identifier-style callbacks and return 400 otherwise.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 6.1 | Medium | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0024, the 15th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 28 Oct 2026, 19:35 UTC Confirmed by the CVE List
- 28 Oct 2026, 20:17 UTC Confirmed by NVD
- 31 Oct 2026, 14:11 UTC First seen by agentprime
- 31 Oct 2026, 14:11 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-h9g5-28mm-hx3g
- OSV: GHSA-h9g5-28mm-hx3g
- github.com/labstack/echo/security/advisories/GHSA-h9g5-28mm-hx3g
- github.com/labstack/echo/commit/b838391e2eade87ae7e5a09d7bb5087bec271ec1
- github.com/labstack/echo/commit/fc410094b2f3415cf2bf5204082137b205bfd5af
- github.com/labstack/echo
- github.com/labstack/echo/releases/tag/v4.16.0
- github.com/labstack/echo/releases/tag/v5.4.0