CVE-2026-54784
CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality
Description
### Impact When the proof key recovered from the RSTR can be observed by a party that is not the legitimate client, that party can impersonate the authenticated Windows principal for the lifetime of the SCT (default ~10 hours) and decrypt or forge any subsequent WS‑SecureConversation traffic that uses keys derived from the SCT. #### Preconditions Using security mode TransportWithMessageCredential with client credential type Windows, along with session establishment (which triggers use of WS-SecureConversation). ### Patches Fixed in CoreWCF v1.9.1 ### Workarounds Ensure communication is protected by SSL/TLS to prevent capturing of SCT negotiation handshake.
How to fix CVE-2026-54784
To remediate CVE-2026-54784, upgrade the affected package to a fixed version below.
- —upgrade to 1.9.1 or later
Is CVE-2026-54784 being exploited?
No exploitation signal available. Neither CISA KEV nor a current EPSS score has been published for CVE-2026-54784.
Affected packages (1)
- >= 1.9.0, < 1.9.1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.4 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N |