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Fencer Intel
high 8.8

CVE-2026-89320 json

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

published 2mo ago modified 9d ago also EUVD-2026-108654 , GHSA-h6w5-722x-2h3m

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository eclipse-keypont/gose. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
8.8
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 6%
public exploits
0
none known

Summary

`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.

Patch / fix

  • Eclipse Foundation Eclipse KeyPont - GOSE 1.0.0-rc1

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
9d ago

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 6% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/eclipse-keypont/gose/security/advisories/GHSA-h6w5-722x-2h3m referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 8.8 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
CNA 4.0 8.8 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • Eclipse Foundation Eclipse KeyPont - GOSE

Classification

Weakness
  • CWE-354 Improper Validation of Integrity Check Value

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of eclipse-keypont/gose published their own advisory on GitHub. Reviewed sources take precedence over it.