CVE-2026-54901
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 · uneditedOj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.2, Oj::Parser in usual mode does not mark array_class and hash_class references during garbage collection, leading to Use-After-Free. If GC runs after the class is assigned but before a parse, the class object is reclaimed, leaving the parser holding a dangling VALUE. The subsequent parse call dereferences the freed object, producing a segfault. 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 confidenceOj::Parser in 'usual mode' fails to mark array_class and hash_class references during Ruby's garbage collection. When GC runs after a class is assigned but before parsing, the class object gets reclaimed, leaving a dangling VALUE pointer. A subsequent parse operation dereferences this freed memory, causing a segmentation fault.
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 checksWork through these to decide whether this CVE applies to you.
-
Check Oj gem versionRun `gem list oj` or `ruby -e "require 'oj'; puts Oj::VERSION"`Affected if Version is lower than 3.17.2
-
Identify if Oj::Parser is used in usual modeReview code for calls to `Oj.parse` or `Oj::Parser.new` without explicit :mode option (usual mode is the default)Affected if Parsing with default mode and no explicit :mode => :strict or :mode => :compat set
-
Check for array_class or hash_class usageSearch code for Oj.parse/Parser calls that include :array_class or :hash_class optionsAffected if Custom array_class or hash_class options are passed to the parser
-
Verify the code path executes GC before parsingReview if GC.start or any operation triggering garbage collection can occur between array_class/hash_class assignment and actual parsingAffected if GC can run after class assignment but before the parse operation completes
-
Confirm vulnerable code path is reachableTrace application logic to determine if parse with custom classes in usual mode is actually called at runtimeAffected if The vulnerable parse operation with custom classes is executed in the application
Affected if running Oj gem version below 3.17.2 and using the default 'usual mode' with custom array_class or hash_class options, where garbage collection can occur between class assignment and parsing.
Generated from the published advisory. Verify against your own configuration.
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 · scopedUpgrade the Oj gem to version 3.17.2 or later to resolve the Use-After-Free vulnerability.
Oj gem version 3.17.2
- 1. Identify the current version of the Oj gem in your Ruby project by running `gem list oj` or checking your Gemfile.lock
- 2. Run `gem install oj` or `bundle update oj` to upgrade to the latest version
- 3. Verify the upgrade was successful by running `gem list oj` to confirm version 3.17.2 or later is installed
- 4. Run your test suite to ensure the upgrade does not break existing functionality
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation1.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,936.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-54901 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-54901 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data