Use-After-Free in oj (CVE-2026-54897)
Summary
Vulnerability in oj (CVE-2026-54897). Risk of unauthorized operations or information disclosure. Exploitable via each_value. Mitigation: upgrade to 3.17.3 or later.
Original description
The description as published by the source.
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:
// 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…
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-54897 has been found in oj.
Attackers can target a specific entry point like each_value over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade oj to 3.17.3 or later.
If unsure, ask your IT team or search "oj CVE-2026-54897" on the vendor's site.
CVE-2026-54897 (oj) — CWE-416
Attack surface: each_value / each_child / each_leaf / doc.close
Patched: 3.17.3 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Use-after-free (CWE-416) exists in oj. Attackers reach the vulnerable code path via each_value.
Check the vendor advisory for the affected versions of oj. Attack surface: each_value / each_child / each_leaf / doc.close.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 3.17.3.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'oj' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'oj' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
ojを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade oj to 3.17.3ステージング環境で 3.17.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-54897 ruby-oj Fixed in: 3.14.2-1+deb12u1
- Ubuntu UBUNTU-CVE-2026-54897 ruby-oj
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web cve.org