Kysely is a type-safe TypeScript SQL query builder. From 0.26.0 to 0.28.16, DefaultQueryCompiler.visitJSONPathLeg does not escape JSON-path metacharacters (., [, ], *, **, ?). When attacker-controlled input flows into eb.ref(col, '->$').key(input) or .at(input) — including type-safe code where the JSON column is shaped like Record<string, T> so K extends string is the inferred type — every dot becomes a path-leg separator, letting an attacker traverse from the intended key into sibling and child fields the developer never meant to expose. The result is read access (and, in update statements, write access) to JSON sub-fields outside the intended scope across MySQL, PostgreSQL ->$/->>$, and SQLite. This vulnerability is fixed in 0.28.17.

Affected: npm: kysely

## Summary

Kysely 0.28.12 added a `sanitizeStringLiteral()` call inside `DefaultQueryCompiler.visitJSONPathLeg` (commit `0a602bf`, PR #1727) to fix CVE-2026-32763 (`GHSA-wmrf-hv6w-mr66`). The fix only doubles single quotes (`'` → `''`); it does **not** escape JSON-path metacharacters (`.`, `[`, `]`, `*`, `**`, `?`). When attacker-controlled input flows into `eb.ref(col, '->$').key(input)` or `.at(input)` — including type-safe code where the JSON column is shaped like `Record<string, T>` so `K extends string` is the inferred type — every dot becomes a path-leg separator, letting an attacker traverse from the intended key into sibling and child fields the developer never meant to expose. The result is read access (and, in update statements, write access) to JSON sub-fields outside the intended scope across MySQL, PostgreSQL `->$`/`->>$`, and SQLite.

* Project: Kysely — TypeScript SQL query builder (npm `kysely`); affects MySQL, PostgreSQL `->$`/`->>$`, and SQLite dialects. * Source reviewed: `kysely-org/kysely` @ `master` (`73192e4`, version `0.28.16`). * Deployed artefact validated: `kysely@0.28.16` from npm. * Affected file(s): * `src/query-compiler/default-query-compiler.ts` (lines 1611–1639, 1821–1823) * `src/query-builder/json-path-builder.ts` (lines 93–196) * `src/dialect/mysql/mysql-query-compiler.ts` (overrides `sanitizeStringLiteral` but inherits the same behaviour for path legs — escapes `\` and `'`, nothing else) * CWE: CWE-89 — Improper Neutralization of Sp…