Local traffic interception via preclaimed named pipe
Published Jul 8, 2026 · Updated Jul 8, 2026
Race condition in CoreWCF NetNamedPipe before 1.8.1 and in 1.9.0 allows local users to intercept named-pipe traffic during service startup. NamedPipeListener publishes a GUID in shared memory before creating the pipe, while _firstConnection remains false and omits FILE_FLAG_FIRST_PIPE_INSTANCE, so the listener silently attaches to an attacker-preclaimed pipe. Exploitation requires low-privileged local access, reading the shared-memory GUID, and winning the startup race; success exposes and permits alteration of service traffic.
Summary
What happened
Race condition in CoreWCF NetNamedPipe before 1.8.1 and in 1.9.0 allows local users to intercept named-pipe traffic during service startup. NamedPipeListener publishes a GUID in shared memory before creating the pipe, while _firstConnection remains false and omits FILE_FLAG_FIRST_PIPE_INSTANCE, so the listener silently attaches to an attacker-preclaimed pipe. Exploitation requires low-privileged local access, reading the shared-memory GUID, and winning the startup race; success exposes and permits alteration of service traffic.
The record
- CVE
- CVE-2026-54777
- Published
- Jul 8, 2026
- Updated
- Jul 8, 2026
- Vendor
- CoreWCF
- Product
- CoreWCF
- Classifications
- CWE-665, CWE-367, T1565.002
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 8, 2026CVE publishedPublication date reported by the CVE source.
- Jul 8, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 1.8.1
- Affected versionversion=>= 1.9.0, < 1.9.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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