CVE-2026-54696: ruby json Heap-based Buffer Overflow

Vulnerability summary

CVE-2026-54696 is a low (CVSS 3.7) Heap-based Buffer Overflow vulnerability in ruby json. EPSS estimates a 0.38% chance of exploitation in the next 30 days, higher than 30.7% of scored vulnerabilities.

Timeline

1. 30-06-2026
   PublishedVulnerability first disclosed.
2. 01-07-2026
   Last modifiedVulnerability information updated.

Description

Ruby JSON is a JSON implementation for Ruby. Versions 2.9.0 through 2.19.8 are vulnerable to heap buffer overflow when the JSON generator is provided with an oversized streamed object. When streaming to an IO JSON.dump(obj, io) and JSON::State#generate(obj, io) can write past the internal JSON generator buffer when a streamed object contains an attacker-controlled string near 16 KB. Exploitation would result in a reliable process crash/denial of service. This issue has been fixed in version 2.19.9.

• CWE-122Heap-based Buffer OverflowA heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
• CWE-131Incorrect Calculation of Buffer SizeThe product does not correctly calculate the size to be used when allocating a buffer, which could lead to a buffer overflow.
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.