CVE-2026-44635

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.

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.

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: [email protected] 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 Special Elements used in an SQL Command, with CWE-915 / CWE-1284 (improper validation of specified quantity in input) flavours for the JSON-path sub-language.
• OWASP 2021: A03:2021 — Injection.

Vulnerable code

src/query-compiler/default-query-compiler.ts:1625-1639:

protected override visitJSONPathLeg(node: JSONPathLegNode): void {
  const isArrayLocation = node.type === 'ArrayLocation'

  this.append(isArrayLocation ? '[' : '.')      // (1)

  this.append(
    typeof node.value === 'string'
      ? this.sanitizeStringLiteral(node.value)  // (2)
      : String(node.value),
  )

  if (isArrayLocation) {
    this.append(']')
  }
}

src/query-compiler/default-query-compiler.ts:1821-1823:

protected sanitizeStringLiteral(value: string): string {
  return value.replace(LIT_WRAP_REGEX, "''")    // (3)
}

with LIT_WRAP_REGEX = /'/g.

src/query-builder/json-path-builder.ts:151-167:

key<
  K extends any[] extends O
    ? never
    : O extends object
      ? keyof NonNullable<O> & string
      : never,
  O2 = undefined extends O
    ? null | NonNullable<NonNullable<O>[K]>
    : null extends O
      ? null | NonNullable<NonNullable<O>[K]>
      : // when the object has non-specific keys, e.g. Record<string, T>, should infer `T | null`!
        string extends keyof NonNullable<O>
        ? null | NonNullable<NonNullable<O>[K]>
        : NonNullable<O>[K],
>(key: K): TraversedJSONPathBuilder<S, O2> {
  return this.#createBuilderWithPathLeg('Member', key)  // (4)
}

src/query-builder/json-path-builder.ts:169-196:

#createBuilderWithPathLeg(
  legType: JSONPathLegType,
  value: string | number,                                // (5)
): TraversedJSONPathBuilder<any, any> {
  // ...
  return new TraversedJSONPathBuilder(
    JSONPathNode.cloneWithLeg(
      this.#node,
      JSONPathLegNode.create(legType, value),            // (6)
    ),
  )
}

At (1) the compiler emits the path-leg separator — . for member access or [ for array index. At (2) the user-supplied string is run through sanitizeStringLiteral, which at (3) only doubles single quotes ('). Dots, brackets, asterisks, double-asterisks and question marks — every reserved character of the SQL/JSON path mini-language — pass through unmodified.

At (4) .key(K) types K as keyof NonNullable<O> & string. When the JSON column is typed as Record<string, T> (a common shape for free-form metadata blobs) the inferred K is just…

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.

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.

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: [email protected] 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 Special Elements used in an SQL Command, with CWE-915 / CWE-1284 (improper validation of specified quantity in input) flavours for the JSON-path sub-language.
• OWASP 2021: A03:2021 — Injection.

Vulnerable code

src/query-compiler/default-query-compiler.ts:1625-1639:

protected override visitJSONPathLeg(node: JSONPathLegNode): void {
  const isArrayLocation = node.type === 'ArrayLocation'

  this.append(isArrayLocation ? '[' : '.')      // (1)

  this.append(
    typeof node.value === 'string'
      ? this.sanitizeStringLiteral(node.value)  // (2)
      : String(node.value),
  )

  if (isArrayLocation) {
    this.append(']')
  }
}

src/query-compiler/default-query-compiler.ts:1821-1823:

protected sanitizeStringLiteral(value: string): string {
  return value.replace(LIT_WRAP_REGEX, "''")    // (3)
}

with LIT_WRAP_REGEX = /'/g.

src/query-builder/json-path-builder.ts:151-167:

key<
  K extends any[] extends O
    ? never
    : O extends object
      ? keyof NonNullable<O> & string
      : never,
  O2 = undefined extends O
    ? null | NonNullable<NonNullable<O>[K]>
    : null extends O
      ? null | NonNullable<NonNullable<O>[K]>
      : // when the object has non-specific keys, e.g. Record<string, T>, should infer `T | null`!
        string extends keyof NonNullable<O>
        ? null | NonNullable<NonNullable<O>[K]>
        : NonNullable<O>[K],
>(key: K): TraversedJSONPathBuilder<S, O2> {
  return this.#createBuilderWithPathLeg('Member', key)  // (4)
}

src/query-builder/json-path-builder.ts:169-196:

#createBuilderWithPathLeg(
  legType: JSONPathLegType,
  value: string | number,                                // (5)
): TraversedJSONPathBuilder<any, any> {
  // ...
  return new TraversedJSONPathBuilder(
    JSONPathNode.cloneWithLeg(
      this.#node,
      JSONPathLegNode.create(legType, value),            // (6)
    ),
  )
}

At (1) the compiler emits the path-leg separator — . for member access or [ for array index. At (2) the user-supplied string is run through sanitizeStringLiteral, which at (3) only doubles single quotes ('). Dots, brackets, asterisks, double-asterisks and question marks — every reserved character of the SQL/JSON path mini-language — pass through unmodified.

At (4) .key(K) types K as keyof NonNullable<O> & string. When the JSON column is typed as Record<string, T> (a common shape for free-form metadata blobs) the inferred K is just…