CVE-2026-33169Network attack vector

Service interruption via quadratic delimiter regex

Published Mar 23, 2026 · Updated Mar 23, 2026

ReDoS in affected Rails Active Support releases allows remote attackers to interrupt service through crafted long digit strings. NumberToDelimitedConverter passes the integer portion to gsub! with a repeated lookahead expression, causing quadratic work as the digit string grows. Applications must pass attacker-controlled long digit strings to number_to_delimited; sustained requests can occupy application workers without reading or altering data.

CVSS severity6.9
Medium
EPSS probability0.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

ReDoS in affected Rails Active Support releases allows remote attackers to interrupt service through crafted long digit strings. NumberToDelimitedConverter passes the integer portion to gsub! with a repeated lookahead expression, causing quadratic work as the digit string grows. Applications must pass attacker-controlled long digit strings to number_to_delimited; sustained requests can occupy application workers without reading or altering data.

The record

CVE
CVE-2026-33169
Published
Mar 23, 2026
Updated
Mar 23, 2026
Vendor
Rails
Product
Active Support
Classifications
CWE-1333, CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 23, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 7.2.3.1
  2. Affected versionversion=>= 8.0.0.beta1, < 8.0.4.1
  3. Affected versionversion=>= 8.1.0.beta1, < 8.1.2.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Rails · Active Supportversion=< 7.2.3.1; version=>= 8.0.0.beta1, < 8.0.4.1; version=>= 8.1.0.beta1, < 8.1.2.1

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
6.9GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
CWE-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo