GHSA-2CW7-V8FF-P88R

Vulnerability from github – Published: 2026-06-19 19:34 – Updated: 2026-06-19 19:34
VLAI
Summary
Oj: Use-After-Free in Oj::Parser Symbol Key Cache Toggle
Details

Summary

Disabling symbol_keys on a reused Oj::Parser instance triggers a heap use-after-free. When symbol_keys is toggled from true to false, opt_symbol_keys_set frees the internal key cache (cache_free) but does not clear the pointer. The next parse call reads from the freed cache via cache_intern, producing a use-after-free.

Version

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

Details

ext/oj/usual.c, opt_symbol_keys_set:

// usual.c:1043–1051
if (symbol_keys) {
    d->key_cache = cache_create(...);   // allocate
} else {
    cache_free(d->key_cache);           // free — but d->key_cache pointer not NULLed
}

On the next parse call, cache_key → cache_intern reads from d->key_cache which now points to freed memory.

ASAN report:

==145265==ERROR: AddressSanitizer: heap-use-after-free on address 0x50b00001a318
READ of size 8 at 0x50b00001a318 thread T0
    #0 cache_intern            /ext/oj/cache.c:328
    #1 cache_key               /ext/oj/usual.c:161
    #2 close_object            /ext/oj/usual.c:285
    #3 parse                   /ext/oj/parser.c:693
    #4 parser_parse            /ext/oj/parser.c:1408
freed by thread T0 here:
    #0 free
    #1 cache_free              /ext/oj/cache.c:277
    #2 opt_symbol_keys_set     /ext/oj/usual.c:1051
    #3 option                  /ext/oj/usual.c:1111
    #4 parser_missing          /ext/oj/parser.c:1362
0x50b00001a318 is 40 bytes inside freed 112-byte region [fd]fd fd fd fd fd fd fd

Reproduce

require 'oj'
p = Oj::Parser.new(:usual, symbol_keys: true)
p.symbol_keys = false     # frees cache without nulling pointer
p.parse('{"attacker":1}') # UAF: reads freed cache
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c 3.17.2"
      },
      "package": {
        "ecosystem": "RubyGems",
        "name": "oj"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.17.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54899"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-19T19:34:30Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\n\nDisabling `symbol_keys` on a reused `Oj::Parser` instance triggers a heap use-after-free. When `symbol_keys` is toggled from `true` to `false`, `opt_symbol_keys_set` frees the internal key cache (`cache_free`) but does not clear the pointer. The next `parse` call reads from the freed cache via `cache_intern`, producing a use-after-free.\n\n### Version\n\n- **Software**: oj gem\n- **Affected**: all versions with `ext/oj/usual.c`\n- **Latest tested**: 3.17.1 (confirmed present)\n\n### Details\n\n`ext/oj/usual.c`, `opt_symbol_keys_set`:\n\n```c\n// usual.c:1043\u20131051\nif (symbol_keys) {\n    d-\u003ekey_cache = cache_create(...);   // allocate\n} else {\n    cache_free(d-\u003ekey_cache);           // free \u2014 but d-\u003ekey_cache pointer not NULLed\n}\n```\n\nOn the next parse call, `cache_key` \u2192 `cache_intern` reads from `d-\u003ekey_cache` which now points to freed memory.\n\nASAN report:\n```\n==145265==ERROR: AddressSanitizer: heap-use-after-free on address 0x50b00001a318\nREAD of size 8 at 0x50b00001a318 thread T0\n    #0 cache_intern            /ext/oj/cache.c:328\n    #1 cache_key               /ext/oj/usual.c:161\n    #2 close_object            /ext/oj/usual.c:285\n    #3 parse                   /ext/oj/parser.c:693\n    #4 parser_parse            /ext/oj/parser.c:1408\nfreed by thread T0 here:\n    #0 free\n    #1 cache_free              /ext/oj/cache.c:277\n    #2 opt_symbol_keys_set     /ext/oj/usual.c:1051\n    #3 option                  /ext/oj/usual.c:1111\n    #4 parser_missing          /ext/oj/parser.c:1362\n0x50b00001a318 is 40 bytes inside freed 112-byte region [fd]fd fd fd fd fd fd fd\n```\n\n### Reproduce\n\n```ruby\nrequire \u0027oj\u0027\np = Oj::Parser.new(:usual, symbol_keys: true)\np.symbol_keys = false     # frees cache without nulling pointer\np.parse(\u0027{\"attacker\":1}\u0027) # UAF: reads freed cache\n```",
  "id": "GHSA-2cw7-v8ff-p88r",
  "modified": "2026-06-19T19:34:30Z",
  "published": "2026-06-19T19:34:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ohler55/oj/security/advisories/GHSA-2cw7-v8ff-p88r"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ohler55/oj"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Oj: Use-After-Free in Oj::Parser Symbol Key Cache Toggle"
}


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