ghsa-9ppp-w3g4-fh4q
CVSS 8.7 osv_rubygems### Summary `Oj::Doc` iterators (`each_value`, `each_child`, `each_leaf`) are vulnerable to a heap use-after-free. When a Ruby block yielded during iteration calls `doc.close` or `d.close`, the document's heap memory is freed while the C iterator is still running. When control returns from the block, the iterator reads from the freed region, producing a use-after-free accessible from pure Ruby. ### Version - **Software**: oj gem - **Affected**: all versions with `ext/oj/fast.c` - **Latest tested**: 3.17.1 (confirmed present) ### Details The iterators in `ext/oj/fast.c` follow the pattern: ```c // fast.c:1505 (doc_each_child) static VALUE doc_each_child(VALUE self, ...) { ... while (cur != NULL) { rb_yield(...); // ← Ruby block executes here cur = cur->next; // ← cur is now freed if block called close() } } ``` `rb_yield` can invoke arbitrary Ruby code, including calling `close()` on the `Doc` or any child node, which calls `ruby_sized_xfree` on the backing buffer. On return, the C code reads `cur->next` from the freed region. All three iterators are affected. ASAN report (each_child variant): ``` ==253632==ERROR: AddressSanitizer: heap-use-after-free on address 0x5210000bd080 READ of size 8 at 0x5210000bd080 thread T0 #0 doc_each_child /ext/oj/fast.c:1505 0x5210000bd080 is located 896 bytes inside of 4064-byte region [0x5210000bcd00, 0x5210000bdce0) freed by thread T0 here: #0 free #1 ruby_sized_xfree (libruby-3.3.so.3.3) ``` All three iterators trigger the same freed region (`fd` shadow bytes): ``` 0x5210000bd080:[fd]fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd ``` ### Reproduce ```ruby require 'oj' # each_child Oj::Doc.open('[1,2]') { |doc| doc.each_child { |d| d.close } } # each_value Oj::Doc.open('[1,2]') { |doc| doc.each_value { |v| doc.close } } # each_leaf Oj::Doc.open('[1,[2]]') { |doc| doc.each_leaf { |d| d.close } } ```
- Published
- unknown
- Last Modified
- unknown
CVSS details not available.
No product information available.
No linked vulnerabilities found.
{
"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-9ppp-w3g4-fh4q/GHSA-9ppp-w3g4-fh4q.json"
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"aliases": [
"CVE-2026-54897"
],
"database_specific": {
"cwe_ids": [
"CWE-416"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-19T19:36:50Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "### Summary\n\n`Oj::Doc` iterators (`each_value`, `each_child`, `each_leaf`) are vulnerable to a heap use-after-free. When a Ruby block yielded during iteration calls `doc.close` or `d.close`, the document's heap memory is freed while the C iterator is still running. When control returns from the block, the iterator reads from the freed region, producing a use-after-free accessible from pure Ruby.\n\n### Version\n\n- **Software**: oj gem\n- **Affected**: all versions with `ext/oj/fast.c`\n- **Latest tested**: 3.17.1 (confirmed present)\n\n### Details\n\nThe iterators in `ext/oj/fast.c` follow the pattern:\n\n```c\n// fast.c:1505 (doc_each_child)\nstatic VALUE doc_each_child(VALUE self, ...) {\n ...\n while (cur != NULL) {\n rb_yield(...); // ← Ruby block executes here\n cur = cur->next; // ← cur is now freed if block called close()\n }\n}\n```\n\n`rb_yield` can invoke arbitrary Ruby code, including calling `close()` on the `Doc` or any child node, which calls `ruby_sized_xfree` on the backing buffer. On return, the C code reads `cur->next` from the freed region. All three iterators are affected.\n\nASAN report (each_child variant):\n```\n==253632==ERROR: AddressSanitizer: heap-use-after-free on address 0x5210000bd080\nREAD of size 8 at 0x5210000bd080 thread T0\n #0 doc_each_child /ext/oj/fast.c:1505\n0x5210000bd080 is located 896 bytes inside of 4064-byte region [0x5210000bcd00, 0x5210000bdce0)\nfreed by thread T0 here:\n #0 free\n #1 ruby_sized_xfree (libruby-3.3.so.3.3)\n```\n\nAll three iterators trigger the same freed region (`fd` shadow bytes):\n```\n0x5210000bd080:[fd]fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd\n```\n\n### Reproduce\n\n```ruby\nrequire 'oj'\n# each_child\nOj::Doc.open('[1,2]') { |doc| doc.each_child { |d| d.close } }\n# each_value\nOj::Doc.open('[1,2]') { |doc| doc.each_value { |v| doc.close } }\n# each_leaf\nOj::Doc.open('[1,[2]]') { |doc| doc.each_leaf { |d| d.close } }\n```",
"id": "GHSA-9ppp-w3g4-fh4q",
"modified": "2026-09-10T03:51:08.386798324Z",
"published": "2026-06-19T19:36:50Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/ohler55/oj/security/advisories/GHSA-9ppp-w3g4-fh4q"
},
{
"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::Doc Iterators via Reentrant Close"
}