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NVD / CVE Program· CNA GitHub_M

CVE-2026-126080: Active Support: Possible DoS vulnerability in Active Support safe_constantize

Noroxi assessment

Priority: Monitor (action score 30/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.82% (FIRST EPSS); higher than 57.9% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: activesupport (RubyGems) 8.1.4.1, 8.0.5.2.

Low priority for now. Upgrade to activesupport (RubyGems) 8.1.4.1, 8.0.5.2 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Active Support is a collection of utility classes and standard library extensions used by Rails and other Ruby projects. Prior to 8.1.4.1 and 8.0.5.2, when constant lookup raises LoadError, ActiveSupport::Inflector#safe_constantize (and String#safe_constantize) builds a regular expression from the requested constant name without escaping it, so a caller that passes untrusted input lets the attacker choose the source of a pattern that the application compiles. Crafted patterns can trigger defects in Ruby's regular expression compiler, possibly leading to a crash of the server process, and repeated requests could keep the application unavailable. Action Cable passes the channel value of each subscribe command to safe_constantize before any channel lookup, so an unauthenticated client can reach this code when the application mounts Action Cable and accepts connections from untrusted clients without an added authentication check. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Nov 10, 2026
Updated
Nov 10, 2026
EPSS
0.8% · 57th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.8%

CNA vs NVD score

NVD
—
CNA · GitHub_M
7.5
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-126080

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • rails rails

    • >= 8.1, < 8.1.4.1, < 8.0.5.2affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12railsfrom 0—
RubyGemsactivesupportfrom 8.1.0.beta1 · before 8.1.4.18.1.4.1
RubyGemsactivesupportbefore 8.0.5.28.0.5.2

Same product

rails: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-66066Action Pack: Possible arbitrary file read and remote code execution in Active Storage variant processing
    60This week
  • CVE-2026-126082Active Storage: Possible arbitrary file write and read in Active Storage image analysis
    39Monitor
  • CVE-2026-126186Active Storage: Possible arbitrary file read and remote code execution in Active Storage video previews, analysis and image processing
    35Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-126078Nov 10, 2026 · Action View: Possible XSS vulnerability in Action View highlight helper
    24Monitor
  • ← EarlierCVE-2026-126079Nov 10, 2026 · Action View: Possible XSS vulnerability in Action View text helpers
    24Monitor
  • Later →CVE-2026-126081Nov 10, 2026 · Action Pack: Possible Strong Parameters bypass in Parameters#each_key
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
RubyGems:activesupport8.0.5.2Package registry (OSV)
RubyGems:activesupport8.1.4.1Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 12, 2026+1 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-74 · Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Exploit maturity— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records