Ruby json: JSON generator heap buffer overflow when streaming to an IO

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

• CISA KEV Not listed.
• EPSS 0.0041, the 35th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

1. 31 Oct 2026, 15:16 UTC First seen by agentprime
2. 31 Oct 2026, 15:16 UTC Confirmed by OSV

Sources

• GitHub Advisory Database: GHSA-x2f5-4prf-w687
• OSV: GHSA-x2f5-4prf-w687
• github.com/ruby/json/security/advisories/GHSA-x2f5-4prf-w687
• nvd.nist.gov/vuln/detail/CVE-2026-54696
• github.com/ruby/json/commit/996bac686d64e4e3aaeae03b14a7f9ee9695ebdb
• github.com/ruby/json
• github.com/ruby/json/releases/tag/v2.19.9
• github.com/rubysec/ruby-advisory-db/blob/master/gems/json/CVE-2026-54696.yml

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.