# CVE-2026-89320: HmacShaCryptor.Hash never hashes its input — returns constant HMAC_K("") for all inputs, voiding CBC-HMAC JWE integrity

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

`HmacShaCryptor.Hash` never hashed its input. For any input it returned `HMAC_K("")` — the MAC of the empty message under the key. Every AES-CBC-HMAC JWE produced or verified by gose therefore carried an authentication tag that is constant per key and independent of the message, removing ciphertext integrity entirely.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Eclipse Foundation / Eclipse KeyPont - GOSE (github.com/ThalesGroup/gose): ≥ 0.9.0; ≤ 0.13.0-rc1 (affected, semver). Source: CNA: eclipse
- Eclipse Foundation / Eclipse KeyPont - GOSE (github.com/eclipse-keypont/gose): ≥ 0; < 1.0.0-rc1 (affected, semver). Source: CNA: eclipse

## Severity and prioritization

- CVSS 4.0: 8.8 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N; source: CNA: eclipse

- CISA KEV: No listing in collected sources

- EPSS: 0.17% as of 2026-11-01; percentile 6.87%

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

- Weaknesses: CWE-354

## Exploit evidence

- exploit: https://github.com/eclipse-keypont/gose/security/advisories/GHSA-h6w5-722x-2h3m (ADP: CISA-ADP)

## References

- https://github.com/eclipse-keypont/gose/security/advisories/GHSA-h6w5-722x-2h3m (CNA: eclipse)

- https://github.com/eclipse-keypont/gose/security/advisories/GHSA-h6w5-722x-2h3m (ADP: CISA-ADP; exploit)

## Provenance

- CNA: eclipse: https://www.cve.org/CVERecord?id=CVE-2026-89320; retrieved 2026-11-02; source updated 2026-11-02

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-89320; retrieved 2026-11-02; source updated Not reported

Revision: 6cf8b6e06655b4ca116de14fb87ccf435bfd6f52a4745892ff62f8eaef27a252

Canonical: https://y2.dev/cve/CVE-2026-89320

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