CVE-2022-36085

OPA Compiler: Bypass of WithUnsafeBuiltins using "with" keyword to mock functions

// VULNERABLE with OPA <= 0.43.0
unsafeBuiltins := map[string]struct{}{
	ast.HTTPSend.Name: struct{}{},
}
compiler := ast.NewCompiler().WithUnsafeBuiltins(unsafeBuiltins)

caps := ast.CapabilitiesForThisVersion()
var j int
for i, bi := range caps.Builtins {
	if bi.Name == ast.HTTPSend.Name {
		j = i
		break
	}
}
caps.Builtins[j] = caps.Builtins[len(caps.Builtins)-1] // put last element into position j
caps.Builtins = caps.Builtins[:len(caps.Builtins)-1]   // truncate slice

compiler := ast.NewCompiler().WithCapabilities(caps)

// VULNERABLE with OPA <= 0.43.0
r := rego.New(
	// other options omitted
	rego.UnsafeBuiltins(map[string]struct{}{ast.HTTPSend.Name: struct{}{}}),
)

r := rego.New(
	// other options omitted
	rego.Capabilities(caps),
)

The Rego compiler provides a (deprecated) WithUnsafeBuiltins function, which allows users to provide a set of built-in functions that should be deemed unsafe, and as such rejected, by the compiler if encountered in the policy compilation stage. A bypass of this protection has been found, where the use of the with keyword to mock such a built-in function (a feature introduced in OPA v0.40.0), isn’t taken into account by WithUnsafeBuiltins.

The same method is exposed via rego.UnsafeBuiltins in the github.com/open-policy-agent/opa/rego package.

When provided e.g. the http.send built-in function to WithUnsafeBuiltins, the following policy would still compile, and call the http.send function with the arguments provided to the is_object function when evaluated:

package policy

foo := is_object({
    "method": "get", 
    "url": "https://www.openpolicyagent.org"
})

allow := r {
    r := foo with is_object as http.send
}

Both built-in functions and user provided (i.e. custom) functions are mockable using this construct.

In addition to http.send, the opa.runtime built-in function is commonly considered unsafe in integrations where policy provided by untrusted parties is evaluated, as it risks exposing configuration, or environment variables, potentially carrying sensitive information.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2022-36085 has a CVSS score of 7.4 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.43.1); upgrading removes the vulnerable code path.

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v0.43.1, v0.44.0

1. What is CVE-2022-36085? CVE-2022-36085 is a high-severity improper input validation vulnerability in github.com/open-policy-agent/opa (go), affecting versions >= 0.40.0, < 0.43.1. It is fixed in 0.43.1. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. How severe is CVE-2022-36085? CVE-2022-36085 has a CVSS score of 7.4 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/open-policy-agent/opa are affected by CVE-2022-36085? github.com/open-policy-agent/opa (go) versions >= 0.40.0, < 0.43.1 is affected.
4. Is there a fix for CVE-2022-36085? Yes. CVE-2022-36085 is fixed in 0.43.1. Upgrade to this version or later.
5. Is CVE-2022-36085 exploitable, and should I be worried? Whether CVE-2022-36085 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2022-36085 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2022-36085? Upgrade github.com/open-policy-agent/opa to 0.43.1 or later.

Other vulnerabilities in github.com/open-policy-agent/opa