Oj: Use-After-Free in Oj::Parser SAJ Callback via Input Mutation
Noroxi assessment
Priority: Monitor (action score 8/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.14% (FIRST EPSS).
- Someone with local access to the system can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- Fixed version: ohler55 oj 3.17.2.
Low priority for now. Upgrade to ohler55 oj 3.17.2 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.2,Oj::Parser#parse is vulnerable to a heap use-after-free when a SAJ/SAJ2 callback mutates the input JSON string during parsing. The C engine holds a raw const byte * pointer into the Ruby string's internal buffer. If a callback (e.g. hash_start) resizes the string — for example by calling String#replace with a longer value — Ruby reallocates the string buffer and frees the old one. The C parser's pointer is left dangling; the next character read at parser.c:607 is a use-after-free. This issue has been fixed in version 3.17.2.
- Published
- Jun 30, 2026
- Updated
- Jul 1, 2026
- EPSS
- 0.1% · 3th percentile
- CWE
- CWE-416
Report tools
Action score
8
Monitor
Low priority for now.
- CVSS
- 8 / 40 · 2.1 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.1%
CISA SSVC decision
- Exploitation
- proof of concept
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · GitHub_M
- 2.1
- NVD has not scored this yet; the score shown is the CNA’s.
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.
ohler55 oj
- < 3.17.2affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | ruby-oj | before 3.14.2-1+deb12u1 | 3.14.2-1+deb12u1 |
| Debian:13 | ruby-oj | before 3.16.3-1+deb13u1 | 3.16.3-1+deb13u1 |
| Debian:14 | ruby-oj | before 3.17.3-1 | 3.17.3-1 |
| RubyGems | oj | before 3.17.3 | 3.17.3 |
Same product
ohler55: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-54592Oj: Stack Buffer Overflow in Oj::Doc#each_child via Deeply Nested Input30Monitor
- CVE-2026-54903Oj: Integer Overflow in Oj.load 2GB String Handling25Monitor
- CVE-2026-54902Oj: Use-After-Free in Oj::Parser SAJ Long Key Callback25Monitor
- CVE-2026-54901Oj: Use-After-Free in Oj::Parser array_class/hash_class GC Marking25Monitor
- CVE-2026-54900Oj: Negative-Size memcpy in Oj::Parser create_id Attribute Handling25Monitor
- CVE-2026-54899Oj: Use-After-Free in Oj::Parser Symbol Key Cache Toggle25Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| ohler55 oj | 3.17.2 · description | Vendor (CNA) |
| debian:ruby-oj | 3.14.2-1+deb12u1 · Debian:12 | Package registry (OSV) |
| debian:ruby-oj | 3.16.3-1+deb13u1 · Debian:13 | Package registry (OSV) |
| RubyGems:oj | 3.17.3 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-548990 days apartOj: Use-After-Free in Oj::Parser Symbol Key Cache Toggle25Monitor
- CVE-2026-549010 days apartOj: Use-After-Free in Oj::Parser array_class/hash_class GC Marking25Monitor
- CVE-2026-549020 days apartOj: Use-After-Free in Oj::Parser SAJ Long Key Callback25Monitor
- CVE-2026-548970 days apartOj : Use-After-Free in Oj::Doc Iterators via Reentrant Close8Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- Integrity
- Availability
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- X
Weakness class (CWE)
CWE-416 · Use After FreeCVSS vector
CVSS:4.0/AV:L/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
nvd-secondary
Root cause
After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.
The bug in code
The whole CWE-416 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);Fixed
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&dev->lock);Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Vendor advisories and official records. Exploit/PoC links are deliberately left out.