# CVE-2026-89315: JwtClaims.MarshalJSON panics via reflect.StructOf when any untyped claim key is not a valid Go identifier suffix

Status: published. Published: 2026-10-23. Updated: 2026-11-02.

`JwtClaims.MarshalJSON` built a Go struct at runtime with `reflect.StructOf`, synthesising a field named `"A" + claimName` for each untyped claim. `reflect.StructOf` **panics** when a field name is not a valid Go identifier, or when it duplicates another field. Both conditions are reachable from ordinary JWT claim names.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Eclipse Foundation / Eclipse KeyPont - GOSE (github.com/ThalesGroup/gose): ≥ 0.7.3; ≤ 0.13.0-rc1 (affected, semver). Source: CNA: eclipse
- Eclipse Foundation / Eclipse KeyPont - GOSE (github.com/eclipse-keypont/gose): ≥ 0; < 1.0.0-rc4 (affected, semver). Source: CNA: eclipse

## Severity and prioritization

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N; source: CNA: eclipse

- CISA KEV: No listing in collected sources

- EPSS: 0.25% as of 2026-11-01; percentile 16.80%

- SSVC: exploitation poc; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-248

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/eclipse-keypont/gose/security/advisories/GHSA-hwm6-rwv6-xgq8 (CNA: eclipse)

## Provenance

- CNA: eclipse: https://www.cve.org/CVERecord?id=CVE-2026-89315; retrieved 2026-11-02; source updated 2026-11-02

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-89315; retrieved 2026-11-02; source updated Not reported

Revision: aef0697c63c79967ec3821c3b8623f7c580a7eb6e25d858400352c5902926200

Canonical: https://y2.dev/cve/CVE-2026-89315