CVE-2021-39155High· 8.3▾ TwilightAuthorization Policy Bypass Due to Case Insensitive Host Comparison
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 45.7 · likelihood 0.2 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 9.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
1.2%
1.2% → 1.2%
Last analysed / modified upstream
According to RFC 4343, Istio authorization policy should compare the hostname in the HTTP Host header in a case insensitive way, but currently the comparison is case sensitive. The Envoy proxy will route the request hostname in a case-insensitive way which means the authorization policy could be bypassed.
As an example, the user may have an authorization policy that rejects request with hostname "httpbin.foo" for some source IPs, but the attacker can bypass this by sending the request with hostname "Httpbin.Foo".
A Lua filter may be written to normalize Host header before the authorization check. This is similar to the Path normalization presented in the Security Best Practices guide.
More details can be found in the Istio Security Bulletin.
If you have any questions or comments about this advisory, please email us at [email protected]
istio.io/istio < 1.9.8istio.io/istio >= 1.10.0, < 1.10.4istio.io/istio >= 1.11.0, < 1.11.1Upgrade to a patched release:
istio.io/istio 1.9.8istio.io/istio 1.10.4istio.io/istio 1.11.1Connected by shared product, vendor, weakness, or advisory.
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