CVE-2026-33169 Rails Active Support has a possible ReDoS vulnerability in number_to_delimited
Attackers can cause denial of service via quadratic time complexity in number_to_delimited when processing long digit strings.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33169?
CVE-2026-33169 is a medium-severity denial of service vulnerability in Rubyonrails Rails, published on 23 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework. `NumberToDelimitedConverter` uses a lookahead-based regular expression with `gsub!` to insert thousands delimiters. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, the interaction between the repeated lookahead group and `gsub!` can produce quadratic time complexity on long digit strings. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.
Which versions are affected by CVE-2026-33169?
6 open source packages ship an affected version, including activesupport. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
activesupport RubyGems | All versions | 7.2.3.1 |
activesupport RubyGems | All versions | 7.2.3.1 |
activesupport RubyGems | From 8.0.0.beta1 | 8.0.4.1 |
activesupport RubyGems | From 8.0.0.beta1 | 8.0.4.1 |
activesupport RubyGems | From 8.1.0.beta1 | 8.1.2.1 |
activesupport RubyGems | From 8.1.0.beta1 | 8.1.2.1 |
Products include Rubyonrails Rails.
How do I fix CVE-2026-33169?
Upgrade activesupport to a fixed version for your release line: 7.2.3.1, 8.0.4.1 or 8.1.2.1.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-33169 being exploited?
There is no known exploitation of CVE-2026-33169 in the wild and no public exploit code.
Other vulnerabilities in Rubyonrails Rails
- CVE-2013-0277 Active Record contains deserialization of arbitrary YAML
- CVE-2017-17916 SQL injection in n/a
- CVE-2017-17917 SQL injection in n/a
- CVE-2026-33195 Rails Active Storage has possible Path Traversal in DiskService
- CVE-2024-26142 Rails possible ReDoS vulnerability in Accept header parsing in Action Dispatch
Sources
Also known as DEBIAN-CVE-2026-33169, GHSA-cg4j-q9v8-6v38, MINI-362p-6cfj-j3mc, MINI-j39f-8jc6-5584, MINI-m8fj-m3qc-xfhm, UBUNTU-CVE-2026-33169.