Oj: intern.c form_attr (uninitialized stack read)

Exploitation

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

CVSS

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

EPSS

• CVE-2026-54500: 0.20% estimated exploitation activity in the next 30 days; percentile 9.57 (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.load in :object mode reads uninitialized stack memory (and, for long keys, reads out of bounds) when parsing a JSON object whose key is 254 bytes or longer. The interned bytes can surface to the caller, disclosing process stack memory. Details In ext/oj/intern.c, formattr() handles the long-key path by allocating a heap buffer b, populating it with the attribute name, and then freeing it — but it passed the uninitialized stack buffer buf (not b) to rbintern3(): rbintern3 therefore reads len + 1 bytes of uninitialized stack memory. When the key length is = 256, it also reads out of bounds past the 256-byte buf (CWE-125). The resulting bytes are interned and can reach the caller via the produced Symbol or via the EncodingError message raised on invalid UTF-8, leaking process stack contents. This is the same defect previously fixed in ext/oj/usual.c; intern.c held a duplicated copy of formattr that was missed. Proof of Concept On affected versions this raises an EncodingError…

Published by the source

19 Jun 2026, 19:35 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-fm7p-mprw-wjm9

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# Patch Next advisory brief: CVE-2026-54500

Advisory: Oj: intern.c form_attr (uninitialized stack read)
IDs: CVE-2026-54500, GHSA-fm7p-mprw-wjm9
Record: https://patchnext.com/advisories/cve-2026-54500 (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: Medium (CVSS 5.3)
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-fm7p-mprw-wjm9 (GitHub-reviewed advisory GHSA-fm7p-mprw-wjm9 lists affected ranges: RubyGems oj >=0 <3.17.3)

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