Oj: Use-After-Free in Oj::Doc Iterators via Reentrant Close

Exploitation

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

CVSS 4.0

8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-54897: 0.20% estimated exploitation activity in the next 30 days; percentile 10.35 (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 iterators (eachvalue, eachchild, eachleaf) 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: rbyield can invoke arbitrary Ruby code, including calling close() on the Doc or any child node, which calls rubysizedxfree on the backing buffer. On return, the C code reads cur-next from the freed region. All three iterators are affected. ASAN report (eachchild variant): All three iterators trigger the same freed region (fd shadow bytes): Reproduce

Published by the source

19 Jun 2026, 19:36 UTC

Last modified by the source

6 Oct 2026, 19:50 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-9ppp-w3g4-fh4q

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# Patch Next advisory brief: CVE-2026-54897

Advisory: Oj: Use-After-Free in Oj::Doc Iterators via Reentrant Close
IDs: CVE-2026-54897, GHSA-9ppp-w3g4-fh4q
Record: https://patchnext.com/advisories/cve-2026-54897 (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 8.7)
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 <= 3.17.2; 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-9ppp-w3g4-fh4q (GitHub-reviewed advisory GHSA-9ppp-w3g4-fh4q lists affected ranges: RubyGems oj >=0 <=3.17.2)

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