Internal network access via unvalidated ACME targets
Published Jul 30, 2026 · Updated Jul 30, 2026
SSRF in Red Hat Certificate System's ACME responder allows remote attackers to send HTTP GET requests to internal services. The HTTP-01 validator accepts IP literals as DNS identifiers and follows redirects without rejecting private, loopback, or link-local targets. Exploitation requires an explicitly deployed ACME responder and an unauthenticated ACME account; supported backends expose network topology, while InMemory also returns internal response bodies in challenge errors.
Summary
What happened
SSRF in Red Hat Certificate System's ACME responder allows remote attackers to send HTTP GET requests to internal services. The HTTP-01 validator accepts IP literals as DNS identifiers and follows redirects without rejecting private, loopback, or link-local targets. Exploitation requires an explicitly deployed ACME responder and an unauthenticated ACME account; supported backends expose network topology, while InMemory also returns internal response bodies in challenge errors.
The record
- CVE
- CVE-2026-18369
- Published
- Jul 30, 2026
- Updated
- Jul 30, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat Enterprise Linux 6
- Classifications
- CWE-918, T1046
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 30, 2026CVE publishedPublication date reported by the CVE source.
- Jul 30, 2026Record updatedLatest update available in the CVE record.
Exploitability
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What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
Your stack
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Your stack
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