Oj: Stack Buffer Overflow in Oj::Doc#each_child via Deeply Nested Input

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-54592: 0.33% estimated exploitation activity in the next 30 days; percentile 25.91 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Oj::Doc#eachchild, 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: 1. doceachchild (~line 1501) increments doc-where past the wherepath[MAXSTACK = 100] array with no bounds check, and never restores it (doc-where-- is missing). Calling eachchild recursively from inside the yield block therefore drives doc-where beyond the array. 2. On the next entry (~line 1478) the function copies the path into a stack-local buffer: When the previous recursive call left doc-where past wherepath[100], wlen exceeds MAXSTACK and the memcpy overflows savepath on 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 Recursion depth <= 99 iterates normally; depth = 101 aborts. lldb backtrace on the affected…

Published by the source

19 Jun 2026, 19:36 UTC

Last modified by the source

19 Jun 2026, 19:36 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-3m6q-jj5j-38c9

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# Patch Next advisory brief: CVE-2026-54592

Advisory: Oj: Stack Buffer Overflow in Oj::Doc#each_child via Deeply Nested Input
IDs: CVE-2026-54592, GHSA-3m6q-jj5j-38c9
Record: https://patchnext.com/advisories/cve-2026-54592 (revision 1, source checked 26 Oct 2026, 15:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: oj 3.17.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems oj: affected < 3.17.3; fixed in 3.17.3

## Suggested inspection (read-only)
- RubyGems oj: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on oj.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-3m6q-jj5j-38c9 (GitHub-reviewed advisory GHSA-3m6q-jj5j-38c9 lists affected ranges: RubyGems oj >=0 <3.17.3)

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