Vulnerability in oj (CVE-2026-54896)
Summary
Vulnerability in oj (CVE-2026-54896). Risk of unauthorized operations or information disclosure. Exploitable via Oj.dump. Mitigation: upgrade to 3.17.3 or later.
Original description
The description as published by the source.
Summary
Oj.dump in object mode is vulnerable to a heap buffer overflow when serializing Exception objects with a large :indent value. The serializer allocates a buffer sized for the object's attributes but does not account for the indent bytes added on each write. With indent: 5000, the accumulation of 5,000-byte indent strings overflows the 13,150-byte heap allocation, corrupting adjacent heap memory.
Version
- Software: oj gem
- Affected: all versions with
ext/oj/dump.h - Latest tested: 3.17.1 (confirmed present)
Details
ext/oj/dump.h, line 75–77:
static void fill_indent(Out out, int depth) {
if (0 < out->opts->indent) {
memset(out->buf + out->cur, ' ', (size_t)(out->opts->indent * depth));
When dumping an Exception object in :object mode, dump_obj_attrs calls fill_indent repeatedly for each attribute. The buffer is pre-allocated based on the serialized content but not the indentation overhead. With indent: 5000 the indent block for a nested object exceeds the remaining buffer space, producing a heap-buffer-overflow of size 5,000 at the end of the allocated region.
ASAN report:
==101656==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x527000022c5e
WRITE of size 5000 at 0x527000022c5e thread T0
#0 memset
#1 fill_indent /ext/oj/dump.h:77
#2 dump_obj_attrs /ext/oj/dump_object.c:552
#3 dump_obj /ext/oj/dump_object.c:80
#4 oj_dump_obj_val /ext/oj/dump_obj…
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-2026-54896 has been found in oj.
Attackers can target a specific entry point like Oj.dump 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-2026-54896" on the vendor's site.
CVE-2026-54896 (oj) — CWE-122
Attack surface: Oj.dump / dump_obj_attrs / fill_indent
Patched: 3.17.3 — apply immediately
Workaround: This is at the discretion of the developer and not a public facing option so the workaround is the develop should not use extreme indents and should not offer the option for users to dump Ruby data with unlimited indentation size.
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.
A vulnerability (CWE-122) exists in oj. Attackers reach the vulnerable code path via Oj.dump.
Check the vendor advisory for the affected versions of oj. Attack surface: Oj.dump / dump_obj_attrs / fill_indent.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 3.17.3.
Workaround: This is at the discretion of the developer and not a public facing option so the workaround is the develop should not use extreme indents and should not offer the option for users to dump Ruby data with unlimited indentation size.
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 temporary workaround mitigate
This is at the discretion of the developer and not a public facing option so the workaround is the develop should not use extreme indents and should not offer the option for users to dump Ruby data with unlimited indentation size.パッチが適用されるまでの応急処置として、This is at the discretion of the developer and not a public facing option so the workaround is the develop should not use extreme indents and should not offer the option for users to dump Ruby data with unlimited indentation size. を実施。回避策の副作用 (機能低下) を確認した上で。
-
3Apply 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。
-
4Post-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-2026-54896 ruby-oj Fixed in: 3.14.2-1+deb12u1
- Ubuntu UBUNTU-CVE-2026-54896 ruby-oj
References
- package github.com
- web github.com
- web github.com