Vulnerability in oj (CVE-2026-54903)
Summary
Vulnerability in oj (CVE-2026-54903). Risk of unauthorized operations or information disclosure. Exploitable via Oj.load. Mitigation: upgrade to 3.17.3 or later.
Original description
The description as published by the source.
Summary
Oj.load is vulnerable to heap corruption when parsing a JSON string longer than 2 GB. An integer overflow in buf_append_string (buf.h:61) converts the string length to a large negative size_t, causing memcpy to copy an astronomically large amount of data out of bounds. This crashes the process and can corrupt adjacent heap memory.
Version
- Software: oj gem
- Affected: all versions with
ext/oj/buf.handext/oj/parse.c - Latest tested: 3.17.1 (confirmed present)
Details
ext/oj/buf.h, line 61:
inline static void buf_append_string(Buf buf, const char *s, size_t slen) {
// ...
memcpy(buf->tail, s, slen); // slen derived from 32-bit int that wrapped negative
In parse.c, escape sequence handling computes the remaining string length as an int:
// parse.c:402 (read_escaped_str)
int slen = (int)(s - str); // ← wraps to negative when string > 2 GB
buf_append_string(buf, str, (size_t)slen); // ← (size_t)(-2147483648) = 0x80000000...
ASAN report:
==399019==ERROR: AddressSanitizer: negative-size-param: (size=-2147483648)
#0 __asan_memcpy
#1 buf_append_string /ext/oj/buf.h:61
#2 read_escaped_str /ext/oj/parse.c:402
#3 read_str /ext/oj/parse.c:542
#4 oj_parse2 /ext/oj/parse.c:882
#5 oj_pi_parse /ext/oj/parse.c:1256
#6 oj_object_parse /ext/oj/object.c:701
#7 load /ext/oj/oj.c:1259
0x7f5a26ff0801 is located 1 bytes insid…
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-2026-54903 has been found in oj.
Attackers can target a specific entry point like Oj.load 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-2026-54903" on the vendor's site.
CVE-2026-54903 (oj) — CWE-190
Attack surface: Oj.load / buf_append_string / size_t / memcpy
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.
A vulnerability (CWE-190) exists in oj. Attackers reach the vulnerable code path via Oj.load.
Check the vendor advisory for the affected versions of oj. Attack surface: Oj.load / buf_append_string / size_t / memcpy.
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-2026-54903 ruby-oj Fixed in: 3.14.2-1+deb12u1
- Ubuntu UBUNTU-CVE-2026-54903 ruby-oj
References
- package github.com
- web github.com
- web github.com