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Use After FreeWeakness · CWE-416

CVE-2026-54902

MEDIUM · 6.3 CVSS v4.0 Published 2026-07-01
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
72/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click 7 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. Prior to version 3.17.2, is vulnerable to Use-After-Free when in SAJ mode. The Oj::Parser does not protect cached object keys (≥ 35 bytes) from garbage collection, and a Ruby callback that triggers GC inside hash_end can cause the key string to be reclaimed while the C parser still holds a pointer to it. The subsequent access to the freed string VALUE results in a segfault, confirmed by an RIP pointing to address 0x4242 (a canary-style pattern suggesting control over the freed memory's content). This issue has been fixed in version 3.17.2.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The Oj Ruby gem versions prior to 3.17.2 have a Use-After-Free vulnerability in SAJ (Special AjMode) parsing mode. The C parser caches object keys >= 35 bytes but fails to protect these cached strings from Ruby's garbage collector. When a Ruby callback triggers GC inside hash_end, the key string can be reclaimed while the C parser still holds a pointer to it, causing a segfault with RIP pointing to 0x4242.

MitigationUpgrade the Oj gem to version 3.17.2 or later. If SAJ mode cannot be updated immediately, avoid Ruby callbacks inside hash_end that could trigger garbage collection.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
Authentication
X
User interaction
None
Scope
X

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Oj gem version
    Run `gem list oj` or `ruby -e "require 'oj'; puts Oj::VERSION"` to retrieve the installed version
    Affected if Version is lower than 3.17.2 (e.g., 3.17.1, 3.16.0, etc.)
  2. Confirm SAJ parsing mode is in use
    Review your Oj parsing code for the :saj or :aj_mode option set to true, or inspect any custom parser configuration that enables Special AjMode
    Affected if SAJ mode (Special AjMode) is enabled in your Oj parser configuration
  3. Identify Ruby callbacks in hash parsing
    Search your codebase for Oj parse calls that use :symbol_keys or custom object handlers that may execute Ruby code during hash_end processing
    Affected if Ruby callbacks or custom handlers execute during hash parsing that could trigger garbage collection
  4. Check for object keys >= 35 bytes in parsed data
    Review or log the JSON data being parsed by Oj in SAJ mode to determine if any hash keys exceed 35 bytes in length
    Affected if Your application parses JSON with hash keys that are 35 bytes or longer while using SAJ mode

You are affected if your installed Oj gem version is below 3.17.2 AND you use SAJ parsing mode with JSON data containing keys >= 35 bytes and have Ruby callbacks that could trigger GC during hash_end processing.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade the Oj gem to version 3.17.2 or later. If SAJ mode cannot be updated immediately, avoid Ruby callbacks inside hash_end that could trigger garbage collection.

Recommended fix High confidence

3.17.2

  1. Run `gem install oj` or add `gem 'oj', '~> 3.17'` to your Gemfile to upgrade to the fixed version
  2. Run `bundle update oj` if using Bundler to fetch the updated gem
  3. Verify the installed version with `gem list oj` to confirm version 3.17.2 or later is installed
  4. If using Bundler, run `bundle exec ruby -e "require 'oj'; puts Oj::VERSION"` to verify the version loaded in your application
Caveat Minimal risk - this is a security patch release; review the Oj gem changelog for any minor behavior changes between your current version and 3.17.2

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-54902 in production — separate from our analysis above.

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What belongs here
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