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certfr-2026-avi-0958 — De multiples vulnérabilités ont été découvertes dans les produits IBM. Certaines d'entre elles permettent à un attaquan…

certfr-2026-avi-0958

EUVD-2026-331604

fkie_cve-2026-54901

Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.2, Oj::Parser in usual mode does not mark array_class and hash_class references during garbage collection, leading to Use-After-Free. If GC runs after the class is assigned but before a parse, the class object is reclaimed, leaving the parser holding a dangling VALUE. The subsequent parse call dereferences the freed object, producing a segfault. This issue has been fixed in version 3.17.2.

GHSA-vwm4-62gf-x745 — Oj: Use-After-Free in Oj::Parser array_class/hash_class GC Marking

Affected: RubyGems: oj

### Summary

`Oj::Parser` in usual mode does not mark `array_class` and `hash_class` references during garbage collection. If GC runs after the class is assigned but before a parse, the class object is reclaimed, leaving the parser holding a dangling VALUE. The subsequent `parse` call dereferences the freed object, producing a segfault.

### Version

- **Software**: oj gem - **Affected**: all versions with `ext/oj/usual.c` / `ext/oj/parser.c` - **Latest tested**: 3.17.1 (confirmed present)

### Details

The `parser_mark` function in `ext/oj/parser.c` is registered as the GC mark callback for the parser's `TypedData`. If `array_class` (stored as `d->array_class` in the `Usual` struct) is not passed to `rb_gc_mark`, the GC does not know it is referenced and may collect it.

When `close_array_class` (`usual.c:405`) later calls `rb_funcallv` on the collected class VALUE, it accesses freed memory, crashing at `RIP: 0x7f... / 0x0000000000000000`.

Crash output: ``` array_class finalized about to parse [BUG] Segmentation fault at 0x0000000000000000 close_array_class+0x194 /ext/oj/usual.c:405 parse+0x17b3 /ext/oj/parser.c:715 parser_parse+0x10b /ext/oj/parser.c:1408 RIP: 0x7fd1b46d68b7 RBP: 0x0000000000000000 ```

### Reproduce

```ruby require 'oj' p = Oj::Parser.new(:usual, array_class: (ac = Class.new { def <<(_x); end })) ObjectSpace.define_finalizer(ac, proc { warn 'array_class finalized' }) ac = nil GC.start(full_mark: true, immediate_sweep: t…

UBUNTU-CVE-2026-54901

Affected: Ubuntu:14.04:LTS: ruby-oj, Ubuntu:16.04:LTS: ruby-oj, Ubuntu:18.04:LTS: ruby-oj, Ubuntu:20.04:LTS: ruby-oj, Ubuntu:22.04:LTS: ruby-oj, Ubuntu:24.04:LTS: ruby-oj, Ubuntu:25.10: ruby-oj, Ubuntu:26.04:LTS: ruby-oj