CVE-2026-11745: Central Dogma SSH Host-key Verification Permanently Disabled Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-vjfw-cpmh-xwv3",
  "modified" : "2026-09-11T20:45:50Z",
  "published" : "2026-09-11T20:45:50Z",
  "aliases" : [ "CVE-2026-11745" ],
  "summary" : "Central Dogma: SSH host-key verification permanently disabled in Git mirror (SshGitMirror)",
  "details" : "# Vulnerability\n\nCentral Dogma's Git mirror SSH client installs an Apache MINA SSHD `ServerKeyVerifier` lambda that returns `true` unconditionally for every outbound SSH connection used by `git+ssh://` mirrors. The accompanying lines disable the `known_hosts` and `~/.ssh/config` fallbacks, and a repo-wide search confirms that no host-key pinning mechanism (no `acceptedHostKeys`, `knownHosts`, `KnownHostsServerKeyVerifier`, `StaticServerKeyVerifier`, or `RequiredServerKeyVerifier`) exists anywhere in `server-mirror-git/`. Operators have no opt-in way to enable verification. Every outbound mirror connection blindly trusts whatever host key the remote presents.\n\n## Evidence\n\nFile: `server-mirror-git/src/main/java/com/linecorp/centraldogma/server/internal/mirror/SshGitMirror.java`\nLines 143-160 (especially 149) on branch `main` @ commit `d64a5151`:\n\n```java\nprivate SshClient createSshClient() {\n    final ClientBuilder builder = ClientBuilder.builder();\n    // Do not use local file system.\n    builder.hostConfigEntryResolver(HostConfigEntryResolver.EMPTY);   // line 146\n    builder.fileSystemFactory(NoneFileSystemFactory.INSTANCE);        // line 147\n    // Do not verify the server key.\n    builder.serverKeyVerifier((clientSession, remoteAddress, serverKey) -> true);  // line 149\n    ...\n}\n```\n\nVerification:\n\n- Read confirmed on 2026-05-21 against `main` @ `d64a5151`.\n- A multi-agent code audit verified that no operator-facing pinning field exists on `SshKeyCredential`, `PasswordCredential`, or `MirrorContext`.\n- Exploit PoC reproduced locally with a `paramiko`-based fake SSH server bound to 127.0.0.1. The fake server presents an ephemeral RSA host key never seen before; the Central Dogma mirror client accepts the connection and proceeds to authentication, logging the offered username and public-key fingerprint. A correctly hardened SSH client would refuse the connection before reaching the authentication phase.\n- Full PoC artifacts (read-only, loopback-only) at `~/centraldogma-poc/C1_ssh_hostkey_bypass/` on the reporter's workstation.\n\n## Impact\n\nThreat model: An on-path attacker on the corporate network — ARP spoofing on the LAN, internal DNS poisoning, malicious internal DNS overriding `github.com` or the configured internal git hostname, BGP hijack, sidecar/CNI compromise in Kubernetes, or any process able to answer TCP on the resolved IP. No Central Dogma account required; only network position.\n\n1. **Direction `LOCAL_TO_REMOTE`**: the attacker impersonating the remote git server receives the entire mirrored repository contents over the SSH session. Central Dogma is a configuration store, so this typically exfiltrates DB credentials, third-party API keys, certificates, feature flags, and any other secret configuration committed to mirrored repositories.\n2. **Direction `REMOTE_TO_LOCAL`**: the attacker can serve arbitrary commits which Central Dogma materializes into the local repo and then broadcasts to every subscribing microservice via the watch API. This is a supply-chain root-of-trust compromise across all downstream services consuming Central Dogma configuration.\n3. **Credential theft chain with finding H2** (mirror credentials are not bound to a hostname): an SSH key or access token configured for `github.com` can be captured by the attacker's fake server and replayed against the real upstream, extending impact beyond Central Dogma itself.\n\nScope is `Changed` (CVSS) because exploitation alters trust assumptions of every downstream client of Central Dogma, not just Central Dogma itself.\n\n## How to fix\n\n1. Add an `acceptedHostKeys: List<String>` field to `SshKeyCredential` and `PasswordCredential` (or to `MirrorContext`). Values are SHA-256 fingerprints of trusted remote SSH server host keys, e.g. `SHA256:nThbg6kXUpJWGl7E1IGOCspRomTxdCARLviKw6E5SY8`.\n2. Replace the accept-all lambda at `SshGitMirror.java:149` with a verifier that computes the SHA-256 fingerprint of the presented host key and compares it against the credential's allowlist using a constant-time comparison.\n3. Refuse to connect when `acceptedHostKeys` is empty — fail-closed. Do not implement implicit TOFU.\n4. Optionally provide an admin-only `dogma mirror probe-host-key <remote>` tool that performs a single audited connection, prints the server's fingerprint, and prompts the operator to add it to the credential. This makes TOFU an explicit, audited operation.\n5. Update `SshGitMirrorTest.java` and `it/mirror/*` tests to pin a test fingerprint or use the explicit trust-once tool, so the regression cannot silently return.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.linecorp.centraldogma:centraldogma-server-mirror-git"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.84.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/line/centraldogma/security/advisories/GHSA-vjfw-cpmh-xwv3"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-11745"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/line/centraldogma"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-322" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-11T20:45:50Z",
    "nvd_published_at" : "2026-06-22T03:16:42Z"
  }
}