CVE-2026-54903: Oj Integer Overflow Vulnerability

HIGH
Advisory Identifier: GHSA-475m-ph3x-64gp
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CWE-190
Published
Advisory Summary

CVE-2026-54903 is a HIGH integer overflow vulnerability (CWE-190: Integer Overflow or Wraparound) affecting Oj libraries in the RubyGems ecosystem. The issue involves integer overflow in oj.load 2gb string handling. Remediation is available by upgrading affected packages to version 3.17.3.

CVE-2026-54903 at a Glance

CVE Identifier CVE-2026-54903
GHSA Identifier GHSA-475m-ph3x-64gp
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-190: Integer Overflow or Wraparound
Affected Product Oj
Package Ecosystem RubyGems
Published Date
Last Updated

How to Fix CVE-2026-54903

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: 3.17.3 
Upgrade oj to 3.17.3
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-2026-54903, 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 3.17.3), 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-190: Integer Overflow or Wraparound, where the product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. this occurs when an integer value is incremented to a value that is too large to store in the associated representation. when this occurs, the value may become a very small or negative number. 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 `Oj.load` is vulnerable to heap corruption when parsing a JSON string longer than 2 GB. An integer overflow in `buf_append_string` (`buf.h:61`) converts the string length to a large negative `size_t`, causing `memcpy` to copy an astronomically large amount of data out of bounds. This crashes the process and can corrupt adjacent heap memory. ### Version - **Software**: oj gem - **Affected**: all versions with `ext/oj/buf.h` and `ext/oj/parse.c` - **Latest tested**: 3.17.1 (confirmed present) ### Details `ext/oj/buf.h`, line 61: ```c inline static void buf_append_string(Buf buf, const char *s, size_t slen) { // ... memcpy(buf->tail, s, slen); // slen derived from 32-bit int that wrapped negative ``` In `parse.c`, escape sequence handling computes the remaining string length as an `int`: ```c // parse.c:402 (read_escaped_str) int slen = (int)(s - str); // ← wraps to negative when string > 2 GB buf_append_string(buf, str, (size_t)slen); // ← (size_t)(-2147483648) = 0x80000000... ``` ASAN report: ``` ==399019==ERROR: AddressSanitizer: negative-size-param: (size=-2147483648) #0 __asan_memcpy #1 buf_append_string /ext/oj/buf.h:61 #2 read_escaped_str /ext/oj/parse.c:402 #3 read_str /ext/oj/parse.c:542 #4 oj_parse2 /ext/oj/parse.c:882 #5 oj_pi_parse /ext/oj/parse.c:1256 #6 oj_object_parse /ext/oj/object.c:701 #7 load /ext/oj/oj.c:1259 0x7f5a26ff0801 is located 1 bytes inside of 2147483657-byte region [0x7f5a26ff0800, 0x7f5aa6ff0809) ``` ### Reproduce ```ruby require 'oj' n = 1 << 31 # 2 GB json = '"' + ('A' * n) + 'A"' # >2GB JSON string with a trailing escape Oj.load(json) ```

CVE-2026-54903 Affected Oj Versions

1 component(s)
Fixed Versions:
3.17.3
Product / Package Ecosystem Affected Versions Fixed Version
oj
gem/oj
RubyGems
< 3.17.3
3.17.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/ohler55/oj/security/advisories/GHSA-475m-ph3x-64gp
Oj Source Repository REPOSITORY
https://github.com/ohler55/oj

Frequently Asked Questions

What is CVE-2026-54903?
CVE-2026-54903 is a security vulnerability in Oj involving Integer Overflow in Oj.load 2GB String Handling under CWE-190: Integer Overflow or Wraparound.
Which Oj versions are affected?
Affected versions include releases prior to 3.17.3 across affected packages: oj.
What version fixes CVE-2026-54903?
Upgrading to 3.17.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is oj affected?
Yes, oj is affected in releases prior to 3.17.3. Upgrade your dependency to 3.17.3 or later.
What CWE is associated with CVE-2026-54903?
CVE-2026-54903 is classified under CWE-190: Integer Overflow or Wraparound (The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.).
How can I check RubyGems dependencies for CVE-2026-54903?
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-475m-ph3x-64gp",
  "modified" : "2026-06-19T20:47:31Z",
  "published" : "2026-06-19T20:47:31Z",
  "aliases" : [ "CVE-2026-54903" ],
  "summary" : "Oj: Integer Overflow in Oj.load 2GB String Handling",
  "details" : "### Summary\n\n`Oj.load` is vulnerable to heap corruption when parsing a JSON string longer than 2 GB. An integer overflow in `buf_append_string` (`buf.h:61`) converts the string length to a large negative `size_t`, causing `memcpy` to copy an astronomically large amount of data out of bounds. This crashes the process and can corrupt adjacent heap memory.\n\n### Version\n\n- **Software**: oj gem\n- **Affected**: all versions with `ext/oj/buf.h` and `ext/oj/parse.c`\n- **Latest tested**: 3.17.1 (confirmed present)\n\n### Details\n\n`ext/oj/buf.h`, line 61:\n\n```c\ninline static void buf_append_string(Buf buf, const char *s, size_t slen) {\n    // ...\n    memcpy(buf->tail, s, slen);   // slen derived from 32-bit int that wrapped negative\n```\n\nIn `parse.c`, escape sequence handling computes the remaining string length as an `int`:\n\n```c\n// parse.c:402 (read_escaped_str)\nint  slen = (int)(s - str);   // ← wraps to negative when string > 2 GB\nbuf_append_string(buf, str, (size_t)slen);  // ← (size_t)(-2147483648) = 0x80000000...\n```\n\nASAN report:\n```\n==399019==ERROR: AddressSanitizer: negative-size-param: (size=-2147483648)\n    #0 __asan_memcpy\n    #1 buf_append_string  /ext/oj/buf.h:61\n    #2 read_escaped_str   /ext/oj/parse.c:402\n    #3 read_str           /ext/oj/parse.c:542\n    #4 oj_parse2          /ext/oj/parse.c:882\n    #5 oj_pi_parse        /ext/oj/parse.c:1256\n    #6 oj_object_parse    /ext/oj/object.c:701\n    #7 load               /ext/oj/oj.c:1259\n0x7f5a26ff0801 is located 1 bytes inside of 2147483657-byte region [0x7f5a26ff0800, 0x7f5aa6ff0809)\n```\n\n### Reproduce\n\n```ruby\nrequire 'oj'\nn = 1 << 31                         # 2 GB\njson = '\"' + ('A' * n) + 'A\"'  # >2GB JSON string with a trailing escape\nOj.load(json)\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" : "3.17.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "< 3.17.2"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/ohler55/oj/security/advisories/GHSA-475m-ph3x-64gp"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ohler55/oj"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-190" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-19T20:47:31Z",
    "nvd_published_at" : null
  }
}