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Response snapshot Oct 29, 2026, 18:26 UTC

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VulnerabilityGHSA-c33x-vcv4-vg3g

Cedar: JSON template is in scope missing slot-id validation allows link panic and decision divergence

Cedar users must be using all of the following features to be affected by this advisory: JSON format policies, policy templates, and the is in scope condition.

At a glance

Exploited
Not known
Severity
Not scored yet
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: cedar-policy: 4.11.1; cedar-policy: 3.4.3; @cedar-policy/cedar-wasm: 4.11.1; @cedar-policy/cedar-wasm: 3.4.3. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-c33x-vcv4-vg3g (opens a new tab)

What happened

Cedar users must be using all of the following features to be affected by this advisory: JSON format policies, policy templates, and the is in scope condition. This advisory only affects JSON-formatted Cedar policy templates containing is in scope conditions that are malformed according to the Cedar syntax. It does not affect syntactically well-formed policies.

Users of Cedar who author policies in the JSON format were able to write Cedar policies using the is in condition with an incorrect slot identifier in the principal and resource scope constraints (e.g., ?principal in the resource scope constraint) even though this is not allowed when parsing policies from the Cedar policy syntax. Internally, the slot identifiers were silently corrected (e.g. ?resource is placed in the resource scope constraint).

If the policy contains *exactly one slot* in either the principal or resource position, then any attempt to create a linked policy from the template results in an error: the internal representation of the template does not contain the slot identifier as written in the malformed JSON policy (it has been corrected silently), so attempting to fill that slot is an error.

If instead the template is linked using slot identifier expected internally (i.e., not what is written in the JSON template), the linking will initially succeed, but a subsequent invariant violation will cause a panic.

Continue reading

When the template contains *slots in both the principal and resource* position, then both slots will be present in the internal representation: linking succeeds, but with each slot bound to the value intended for the other (the silent correction). The linked policy is then semantically different from the malformed policy the user intended, and any subsequent authorization decision made against that policy may lead to accesses being unintentionally allowed or denied.

Concretely, consider the following JSON format policy template intended to deny users in a particular project from accessing documents with a particular classification.

{
 "effect": "forbid",
 "principal": {
 "op": "is",
 "entity_type": "User",
 "in": { "slot": "?resource" }
 },
 "action": { "op": "All" },
 "resource": {
 "op": "is",
 "entity_type": "Doc",
 "in": { "slot": "?principal" }
 },
 "conditions": []
}

Linked with ?principal = Classification::"topsecret" and ?resource = Project::"alpha", the author expects to create the policy:

forbid(principal is User in Project::"alpha", action, resource is Doc in Classification::"topsecret");

But because Cedar internally links slots by scope position (not by name), the actual policy evaluated by the engine is:

forbid(principal is User in Classification::"topsecret", action, resource is Doc in Project::"alpha");

If a user is in Project::"alpha" but not Classification::"topsecret", the forbid policy does not apply, and access is unintentionally allowed.

Patches

This advisory is patched in version 4.11.1 and 3.4.3, both available on Crates.io and NPM.

Workarounds

If you cannot update to a patched version, you can determine if you are affected by checking your JSON format policy templates for the following two patterns.

 "principal": {
 "op": "is",
 "entity_type": "User",
 "in": { "slot": "?resource" }
 }

and

 "resource": {
 "op": "is",
 "entity_type": "Doc",
 "in": { "slot": "?principal" }
 }

References

* [Cedar Policy Language Reference Guide - Cedar Policy Templates](https://docs.cedarpolicy.com/policies/templates.html) * [Cedar Policy Language Reference Guide - JSON Policy Format](https://docs.cedarpolicy.com/policies/json-format.html)

Affected package ranges reported by GitHub: cedar-policy: >= 4.0.0, < 4.11.1 cedar-policy: >= 3.0.0, < 3.4.3 @cedar-policy/cedar-wasm: >= 4.0.1, < 4.11.1 @cedar-policy/cedar-wasm: >= 3.2.0, < 3.4.3

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-c33x-vcv4-vg3g (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c33x-vcv4-vg3g, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 29). Cedar: JSON template is in scope missing slot-id validation allows link panic and decision divergence. https://kevwire.com/record/GHSA-c33x-vcv4-vg3g

MLA

"Cedar: JSON template is in scope missing slot-id validation allows link panic and decision divergence." KEVWire, 29 Oct. 2026, kevwire.com/record/GHSA-c33x-vcv4-vg3g.

Chicago

KEVWire. "Cedar: JSON template is in scope missing slot-id validation allows link panic and decision divergence." Last modified October 29, 2026. https://kevwire.com/record/GHSA-c33x-vcv4-vg3g.

Evidence summary (plain text)

Cedar: JSON template is in scope missing slot-id validation allows link panic and decision divergence (Oct 29, 2026).
Cedar users must be using all of the following features to be affected by this advisory: JSON format policies, policy templates, and the is in scope condition. This advisory only affects JSON-formatted Cedar policy templates containing is in scope conditions that are malformed according to the Cedar syntax. It does not affect syntactically well-formed policies.
Sources:
GitHub-reviewed advisory GHSA-c33x-vcv4-vg3g: https://github.com/advisories/GHSA-c33x-vcv4-vg3g
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: GHSA-c33x-vcv4-vg3g.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 29, 2026, 18:26 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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