GHSA-r5fr-9gmv-jggh

### Summary A single unauthenticated `GET` to any `/scim/v1/...` endpoint with a `?filter=` query string of a few thousand nested parentheses (≈ 4–12 KB) drives the recursive-descent PEG parser past the worker thread's stack guard page. Rust responds to stack overflow with `std::process::abort()` — the entire `kanidmd` process exits. The parse runs inside axum's `Query<ScimEntryGetQuery>` extractor, before any handler body and therefore before any ACL check. ### Details The SCIM filter grammar recurses on `(` and `not (` with no depth bound. **`proto/src/scim_v1/mod.rs:263-433`** — `peg::parser! { grammar scimfilter() ... }`: ```rust // line 281 "not" separator()+ "(" e:parse() ")" { ScimFilter::Not(Box::new(e)) } // line 293 "(" e:parse() ")" { e } ``` Both rules re-enter `parse()` without a depth counter. **`proto/src/scim_v1/mod.rs:442-447`** — `impl FromStr for ScimFilter` calls `scimfilter::parse(input)` directly on the raw string with no length or depth pre-check. **`proto/src/scim_v1/mod.rs:80-81`** — `ScimEntryGetQuery.filter` is `#[serde_as(as = "Option<DisplayFromStr>")]`, so deserialising the query struct invokes `ScimFilter::from_str` on attacker bytes. **Unauthenticated reachability** — nine handlers in `server/core/src/https/v1_scim.rs` (route table at lines 865-1029) take `Query<ScimEntryGetQuery>` as an argument: `/scim/v1/Entry`, `/scim/v1/Entry/{id}`, `/scim/v1/Person/{id}`, `/scim/v1/Application`, `/scim/v1/Application/{id}`, `/scim/v1/Class`, `/scim/v1/Attribute`, `/scim/v1/Message`, `/scim/v1/Message/{id}`. The SCIM router is merged unconditionally for every server role (`server/core/src/https/mod.rs:312`). Axum extracts handler arguments before the handler body runs. The preceding `VerifiedClientInformation` extractor (`server/core/src/https/extractors/mod.rs:16-91`) always returns `Ok` (line 89) regardless of credentials; authorization is deferred to the handler body, which is never reached. The existing semantic depth limit (`DEFAU