GHSA-3m6q-jj5j-38c9
HIGHGHSA-3m6q-jj5j-38c9 is a high-severity (CVSS 7.5) Out-of-bounds Read vulnerability in oj. O3 Security confirms whether GHSA-3m6q-jj5j-38c9 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Oj: Stack Buffer Overflow in Oj::Doc#each_child via Deeply Nested Input
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-3m6q-jj5j-38c9.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-3m6q-jj5j-38c9 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 359,229 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
ojReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Oj::Doc#each_child, when invoked recursively over a deeply nested JSON
document, overflows a fixed-size stack buffer and aborts the process. This is a
denial of service reachable from untrusted JSON.
Details
Two-step chain in ext/oj/fast.c:
-
doc_each_child(~line 1501) incrementsdoc->wherepast thewhere_path[MAX_STACK = 100]array with no bounds check, and never restores it (doc->where--is missing). Callingeach_childrecursively from inside the yield block therefore drivesdoc->wherebeyond the array. -
On the next entry (~line 1478) the function copies the path into a stack-local buffer:
Leaf save_path[MAX_STACK]; // 800-byte stack buffer size_t wlen = doc->where - doc->where_path; if (0 < wlen) { memcpy(save_path, doc->where_path, sizeof(Leaf) * (wlen + 1)); }When the previous recursive call left
doc->wherepastwhere_path[100],wlenexceedsMAX_STACKand thememcpyoverflowssave_pathon the C stack.
The Oj::Doc parser imposes no JSON nesting-depth limit (it relies on a
C-stack pressure check), so deeply nested attacker input reaches this path.
Proof of Concept
require 'oj'
depth = 200
payload = '[' * depth + '1' + ']' * depth
Oj::Doc.open(payload) do |doc|
r = lambda { doc.each_child { |_| r.call } }
r.call
end
Recursion depth <= 99 iterates normally; depth >= 101 aborts. lldb backtrace
on the affected build (ruby 3.3.8 / arm64-darwin24):
SIGABRT
#2 __abort
#3 __stack_chk_fail
#4 doc_each_child (oj.bundle, fast.c)
Impact
Reliable denial of service: any endpoint that calls
Oj::Doc.open(untrusted) { |d| d.each_child ... } recursively can be crashed
with a small deeply-nested payload. On builds with a stack protector (the
default, -fstack-protector-strong) the canary aborts the process before the
saved return address is used. The Step-1 heap OOB writes into struct _doc
fields do occur, but are masked in practice because the Step-2 stack overflow
crashes first; turning them into anything beyond a crash has not been
demonstrated.
Patches
Fixed in 3.17.3: doc_each_child now bounds-checks before incrementing
doc->where (raising Oj::DepthError) and restores doc->where after the
loop, matching the existing each_leaf pattern. Verified on the fixed build:
depth >= 101 raises a clean Oj::DepthError instead of aborting.
Credit
Reported by Zac Wang (@7a6163).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | oj | all versions | 3.17.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for oj. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update oj to 3.17.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3m6q-jj5j-38c9 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-3m6q-jj5j-38c9 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-3m6q-jj5j-38c9. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-3m6q-jj5j-38c9 in your dependencies?
O3 detects GHSA-3m6q-jj5j-38c9 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.