CVE-2026-126075: rails · Cross-site Scripting
Affects railsSource CVE Database V5
Not known to be exploited · CVSS 4.7 Medium : upgrade to 8.1.4.1 when convenient.
Data as of 10 Nov 2026, 21:17 UTC
Thin evidence
One scorer or none| CNA (GitHub_M) | CVSS 3.1 | 4.7 |
|---|
- Patch
- Available – fixed in 8.1.4.1
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 10 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.
What to do
Upgrade rails to 8.1.4.1.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| railsrails | Affected
| Fixed in
|
AI-suggested
Upgrade affected Rails applications to version 8.1.4.1 or later, where this issue is fixed. If upgrading immediately is not possible, avoid using MessagePack serializers for cookies, cache, or message verification/encryption with mutated SafeBuffer objects containing untrusted input. Review application code to prevent storing mutated SafeBuffer instances with untrusted data. Patch status is confirmed fixed in 8.1.4.1.
Description
A cross-site scripting (XSS) vulnerability exists in Rails versions 8.1 through 8.1.4 prior to 8.1.4.1 in the ActiveSupport::MessagePack serializer. This flaw occurs because mutated SafeBuffer objects containing untrusted input can be restored as html_safe, bypassing ERB auto-escaping and potentially enabling XSS when rendered. The issue affects applications using MessagePack serializers for cookies, cache, or message verification/encryption that store such mutated SafeBuffer instances. Rails 8.0 and earlier are not affected. The vulnerability is fixed in Rails 8.1.4.1.