CVE-2026-54899: Oj Use-After-Free Vulnerability

HIGH
Advisory Identifier: GHSA-2cw7-v8ff-p88r
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CWE-416
Published
Advisory Summary

CVE-2026-54899 is a HIGH use-after-free vulnerability (CWE-416: Use After Free) affecting Oj libraries in the RubyGems ecosystem. The issue involves use-after-free in oj::parser symbol key cache toggle. Remediation is available by upgrading affected packages to version 3.17.2.

CVE-2026-54899 at a Glance

CVE Identifier CVE-2026-54899
GHSA Identifier GHSA-2cw7-v8ff-p88r
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-416: Use After Free
Affected Product Oj
Package Ecosystem RubyGems
Published Date
Last Updated

How to Fix CVE-2026-54899

To remediate this vulnerability, upgrade all affected Oj dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

oj fixed: 3.17.2 
Upgrade oj to 3.17.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for oj

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-54899, inspect your project dependencies for Oj:

inspect dependencies for oj

Analyze the terminal output to locate any version of Oj in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.17.2), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-416: Use After Free, where the product reuses or references memory after it has been freed. at some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer. In Oj, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary Disabling `symbol_keys` on a reused `Oj::Parser` instance triggers a heap use-after-free. When `symbol_keys` is toggled from `true` to `false`, `opt_symbol_keys_set` frees the internal key cache (`cache_free`) but does not clear the pointer. The next `parse` call reads from the freed cache via `cache_intern`, producing a use-after-free. ### Version - **Software**: oj gem - **Affected**: all versions with `ext/oj/usual.c` - **Latest tested**: 3.17.1 (confirmed present) ### Details `ext/oj/usual.c`, `opt_symbol_keys_set`: ```c // usual.c:1043–1051 if (symbol_keys) { d->key_cache = cache_create(...); // allocate } else { cache_free(d->key_cache); // free — but d->key_cache pointer not NULLed } ``` On the next parse call, `cache_key` → `cache_intern` reads from `d->key_cache` which now points to freed memory. ASAN report: ``` ==145265==ERROR: AddressSanitizer: heap-use-after-free on address 0x50b00001a318 READ of size 8 at 0x50b00001a318 thread T0 #0 cache_intern /ext/oj/cache.c:328 #1 cache_key /ext/oj/usual.c:161 #2 close_object /ext/oj/usual.c:285 #3 parse /ext/oj/parser.c:693 #4 parser_parse /ext/oj/parser.c:1408 freed by thread T0 here: #0 free #1 cache_free /ext/oj/cache.c:277 #2 opt_symbol_keys_set /ext/oj/usual.c:1051 #3 option /ext/oj/usual.c:1111 #4 parser_missing /ext/oj/parser.c:1362 0x50b00001a318 is 40 bytes inside freed 112-byte region [fd]fd fd fd fd fd fd fd ``` ### Reproduce ```ruby require 'oj' p = Oj::Parser.new(:usual, symbol_keys: true) p.symbol_keys = false # frees cache without nulling pointer p.parse('{"attacker":1}') # UAF: reads freed cache ```

CVE-2026-54899 Affected Oj Versions

1 component(s)
Fixed Versions:
3.17.2
Product / Package Ecosystem Affected Versions Fixed Version
oj
gem/oj
RubyGems
< 3.17.2
3.17.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/ohler55/oj/security/advisories/GHSA-2cw7-v8ff-p88r
NVD — CVE-2026-54899 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-54899
Oj Source Repository REPOSITORY
https://github.com/ohler55/oj
Oj Source Repository REPOSITORY
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/oj/CVE-2026-54899.yml
CVE Official Record — CVE-2026-54899 CVE
https://www.cve.org/CVERecord/SearchResults?query=CVE-2026-54899

Frequently Asked Questions

What is CVE-2026-54899?
CVE-2026-54899 is a security vulnerability in Oj involving Use-After-Free in Oj::Parser Symbol Key Cache Toggle under CWE-416: Use After Free.
Which Oj versions are affected?
Affected versions include releases prior to 3.17.2 across affected packages: oj.
What version fixes CVE-2026-54899?
Upgrading to 3.17.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is oj affected?
Yes, oj is affected in releases prior to 3.17.2. Upgrade your dependency to 3.17.2 or later.
What CWE is associated with CVE-2026-54899?
CVE-2026-54899 is classified under CWE-416: Use After Free (The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.).
How can I check RubyGems dependencies for CVE-2026-54899?
Run the dependency tree command: 'inspect dependencies for oj'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2cw7-v8ff-p88r",
  "modified" : "2026-10-06T19:52:36Z",
  "published" : "2026-06-19T19:34:30Z",
  "aliases" : [ "CVE-2026-54899" ],
  "summary" : "Oj: Use-After-Free in Oj::Parser Symbol Key Cache Toggle",
  "details" : "### Summary\n\nDisabling `symbol_keys` on a reused `Oj::Parser` instance triggers a heap use-after-free. When `symbol_keys` is toggled from `true` to `false`, `opt_symbol_keys_set` frees the internal key cache (`cache_free`) but does not clear the pointer. The next `parse` call reads from the freed cache via `cache_intern`, producing a use-after-free.\n\n### Version\n\n- **Software**: oj gem\n- **Affected**: all versions with `ext/oj/usual.c`\n- **Latest tested**: 3.17.1 (confirmed present)\n\n### Details\n\n`ext/oj/usual.c`, `opt_symbol_keys_set`:\n\n```c\n// usual.c:1043–1051\nif (symbol_keys) {\n    d->key_cache = cache_create(...);   // allocate\n} else {\n    cache_free(d->key_cache);           // free — but d->key_cache pointer not NULLed\n}\n```\n\nOn the next parse call, `cache_key` → `cache_intern` reads from `d->key_cache` which now points to freed memory.\n\nASAN report:\n```\n==145265==ERROR: AddressSanitizer: heap-use-after-free on address 0x50b00001a318\nREAD of size 8 at 0x50b00001a318 thread T0\n    #0 cache_intern            /ext/oj/cache.c:328\n    #1 cache_key               /ext/oj/usual.c:161\n    #2 close_object            /ext/oj/usual.c:285\n    #3 parse                   /ext/oj/parser.c:693\n    #4 parser_parse            /ext/oj/parser.c:1408\nfreed by thread T0 here:\n    #0 free\n    #1 cache_free              /ext/oj/cache.c:277\n    #2 opt_symbol_keys_set     /ext/oj/usual.c:1051\n    #3 option                  /ext/oj/usual.c:1111\n    #4 parser_missing          /ext/oj/parser.c:1362\n0x50b00001a318 is 40 bytes inside freed 112-byte region [fd]fd fd fd fd fd fd fd\n```\n\n### Reproduce\n\n```ruby\nrequire 'oj'\np = Oj::Parser.new(:usual, symbol_keys: true)\np.symbol_keys = false     # frees cache without nulling pointer\np.parse('{\"attacker\":1}') # UAF: reads freed cache\n```",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "oj"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.17.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/ohler55/oj/security/advisories/GHSA-2cw7-v8ff-p88r"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-54899"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ohler55/oj"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/oj/CVE-2026-54899.yml"
  }, {
    "type" : "WEB",
    "url" : "https://www.cve.org/CVERecord/SearchResults?query=CVE-2026-54899"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-416" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-19T19:34:30Z",
    "nvd_published_at" : "2026-07-01T00:16:33Z"
  }
}