Rails has possible ReDoS vulnerability in Accept header parsing in Action Dispatch

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 0.015, the 74th percentile, on 6 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-jjhx-jhvp-74wq
• OSV: GHSA-jjhx-jhvp-74wq
• github.com/rails/rails/security/advisories/GHSA-jjhx-jhvp-74wq
• nvd.nist.gov/vuln/detail/CVE-2024-26142
• github.com/rails/rails/commit/b4d3bfb5ed8a5b5a90aad3a3b28860c7a931e272
• discuss.rubyonrails.org/t/possible-redos-vulnerability-in-accept-header-parsing-in-action-dispatch/84946
• github.com/rails/rails
• github.com/rubysec/ruby-advisory-db/blob/master/gems/actionpack/CVE-2024-26142.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.