GHSA-cg4j-q9v8-6v38 CVE-2026-33169
Rails Active Support has a possible ReDoS vulnerability in number_to_delimited
Medium
RubyGems
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.66%
- Chance of exploitation in the next 30 days. Higher than 51.41% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Fix
8.1.2.1- Upgrade activesupport to this version or later
Description
Impact
NumberToDelimitedConverter used a regular expression with gsub! to insert thousands delimiters. This could produce quadratic time complexity on long digit strings.
Releases
The fixed releases are available at the normal locations.
Credit
This issue was responsibly reported by Hackerone researcher scyoon.
Affected versions
RubyGems
| Package | Vulnerable | Fixed in |
|---|---|---|
| activesupport | >= 8.1.0.beta1, < 8.1.2.1 |
8.1.2.1 |
| activesupport | >= 8.0.0.beta1, < 8.0.4.1 |
8.0.4.1 |
| activesupport | < 7.2.3.1 |
7.2.3.1 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
activesupport RubyGems → 8.1.2.1
- bundler
bundle update activesupport # Gemfile: gem "activesupport", ">= 8.1.2.1"
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- Low
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
CVSS 3.1 5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Weakness
CWE-1333: Inefficient Regular Expression Complexity
The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
How to prevent it
- Architecture and Design: Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
- System Configuration: Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
- Implementation: Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
- Implementation: Limit the length of the input that the regular expression will process.
CWE-400: Uncontrolled Resource Consumption
The product does not properly control the allocation and maintenance of a limited resource.
How to prevent it
- Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
- Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
- Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
- Implementation: Ensure that all failures in resource allocation place the system into a safe posture.
References
Advisories
Packages
Other links
- github.com/rails/rails/security/advisories/GHSA-cg4j-q9v8-6v38
- github.com/rails/rails/commit/29154f1097da13d48fdb3200760b3e3da66dcb11
- github.com/rails/rails/commit/b54a4b373c6f042cab6ee2033246b1c9ecc38974
- github.com/rails/rails/commit/ec1a0e215efd27a3b3911aae6df978a80f456a49
- github.com/rails/rails/releases/tag/v7.2.3.1
- github.com/rails/rails/releases/tag/v8.0.4.1
- github.com/rails/rails/releases/tag/v8.1.2.1
- github.com/rubysec/ruby-advisory-db/blob/master/gems/activesupport/CVE-2026-331…
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-2j26-frm8-cmj9 Rails Active Support has a possible DoS vulnerability in its number helpers | High | Also affects activesupport |
| GHSA-89vf-4333-qx8v Rails Active Support has a possible XSS vulnerability in SafeBuffer#% | Medium | Also affects activesupport |
| GHSA-cr5q-6q9f-rq6q Active Support Possibly Discloses Locally Encrypted Files | Medium | Also affects activesupport |
| GHSA-pj73-v5mw-pm9j Possible XSS Security Vulnerability in SafeBuffer#bytesplice | Medium | Also affects activesupport |
| GHSA-j6gc-792m-qgm2 ReDoS based DoS vulnerability in Active Support's underscore | Low | Also affects activesupport |
| GHSA-2p68-f74v-9wc6 ActiveSupport potentially unintended unmarshalling of user-provided objects in MemCacheStore and RedisCacheStore | Critical | Also affects activesupport |
| GHSA-qv8p-v9qw-wc7g activesupport Cross-site Scripting vulnerability | Medium | Also affects activesupport |
| GHSA-9fh3-vh3h-q4g3 activesupport Cross-site Scripting vulnerability | Medium | Also affects activesupport |
MergeHarbor checks every repository's dependencies against this database, ranks what matters by exploitability and reachability, routes it to the owning team and opens the fix pull request.
Check your repos with MergeHarbor