GHSA-hcw3-j74m-qc58 is a medium-severity (CVSS 6.3) CWE-682 vulnerability in github.com/open-policy-agent/opa. 1 public exploit reference exists, so weaponization risk is real. A fix is available for github.com/open-policy-agent/opa — see the affected versions and patch details below.
Incorrect Calculation in github.com/open-policy-agent/opa
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for GHSA-hcw3-j74m-qc58.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-hcw3-j74m-qc58 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/open-policy-agent/opaReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Under certain conditions, pretty-printing an AST that contains synthetic nodes could change the logic of some statements by reordering array literals. Example of policies impacted are those that parse and compare web paths, see the example below.
All of these three conditions have to be met to create an adverse effect:
- An AST of Rego had to be created programmatically such that it ends up containing terms without a location (such as wildcard variables).
- The AST had to be pretty-printed using the
github.com/open-policy-agent/opa/formatpackage. - The result of the pretty-printing had to be parsed and evaluated again via an OPA instance using the bundles, or the Golang packages.
If any of these three conditions are not met, you are not affected.
Notably, all three would be true if using optimized bundles, i.e. bundles created with opa build -O=1 or higher.
In that case, the optimizer would fulfil condition (1.), the result of that would be pretty-printed when writing the bundle to disk, fulfilling (2.). When the bundle was then used, we'd satisfy (3.).
Example
For example, the process outlined above could turn this rule
hello {
["foo", _] = split(input.resource, "/")
}
into
hello {
[_, "foo"] = split(input.resource, "/")
}
with an input of
{
"resource": "foo/bar"
}
the result would change from
{
"hello": true
}
to (no default value of hello)
{}
The severity was determined to be moderate because the conditions are quite particular. Please note that its only the OPA bundle build process thats affected. An OPA sidecar of version 0.36.0 with an optimized bundle built by OPA 0.32.1 would not face this bug.
Patches
Fixed in version 0.37.2.
Workarounds
- Disabling optimization when creating bundles.
References
- Introduced in https://github.com/open-policy-agent/opa/pull/3851
- Backported for the 0.33.1 patch release: https://github.com/open-policy-agent/opa/commit/bfd984ddf93ef2c4963a08d4fdadae0bcf1a3717
- Fixed by https://github.com/open-policy-agent/opa/commit/932e4ffc37a590ace79e9b75ca4340288c220239 and https://github.com/open-policy-agent/opa/commit/2bd8edab9e10e2dc9cf76ae8335ced0c224f3055
For more information
If you have any questions or comments about this advisory:
- Open an issue in Community Discussions
- Ask in Slack: https://slack.openpolicyagent.org/
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/open-policy-agent/opa | ≥ 0.33.1&&< 0.37.2 | 0.37.2go get github.com/open-policy-agent/opa@v0.37.2 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/open-policy-agent/opa, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/open-policy-agent/opa to 0.37.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hcw3-j74m-qc58 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-hcw3-j74m-qc58 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-hcw3-j74m-qc58. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-hcw3-j74m-qc58 in your dependencies?
O3 Security finds GHSA-hcw3-j74m-qc58 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.