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CVE-2026-126083

Action Pack: Possible IP spoofing in Action Dispatch RemoteIp

Products / packages rails · actionpack

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Severity and exploitation

Not in CISA KEVSource: HIGH

KEV coverage does not rule out exploitation.

KEV checked 14/11/2026, 23:05:32 UTC
OSV · CVSS:3.0 · 7.4
Assessment vectorCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
GitHub_M · CVSS:3.0 · 7.4
Assessment vectorCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
The headline uses the highest imported catalog score. Assessments can differ by source and CVSS version.

Severity

high7.4

CVSS measures technical severity, not the likelihood of an attack.

Known exploitation

Not listed in the checked CISA KEV catalog

Absence from CISA KEV does not rule out attacks.

Public exploit

Not established by this record

Missing evidence does not mean no public exploit exists.

Remediation

Package fixes recorded

Fix versions are recorded for 1 of 1 mapped packages. Check each release branch and any separate product guidance.

What this means

Action Pack in Rails 8.1.0 through 8.1.4 is vulnerable to IP spoofing when a reverse proxy appends the client address to X-Forwarded-For but passes a client-supplied Forwarded header through unchanged. An unauthenticated attacker could spoof request.remote_ip, possibly bypassing IP-based access controls. The weakness is due to the use of a less trusted source.

Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.

Attack conditions

No attack-condition excerpt has been identified here. Review the full source description and references for authentication, network access, and configuration requirements.

Review supporting sources →

Affected versions

Check the exact model, release, and any platform requirements against your installation.

rails · GitHub_M

rails

1 range
GitHub_M version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

>= 8.1, < 8.1.4.1

unaffected

unknown

Other versions: unknown

Packages

Compare each installed version with the publisher’s affected ranges. Where a fix is recorded, choose the appropriate release branch and test compatibility before upgrading.

actionpack RubyGems
Affected range Recorded fix
From 8.1.0.beta1 before 8.1.4.1Ecosystem versions8.1.4.1

Version evidence: OSV · GHSA-2gff-2mmg-m73p

View original version evidence (9 explicit versions)

What to do

Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.

Use the recorded fix for your release branch. Review the publisher’s instructions and test compatibility before upgrading.

cve.new guidance unless attributed to a publisher. This page does not inspect your installation.

Public exploit evidence

No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.

Original source description

Read the full publisher description

Impact

Since Rails 8.1.0, ActionDispatch::RemoteIp derives request.remote_ip from Rack::Request#forwarded_for, which under Rack 3 reads the RFC 7239 Forwarded header in preference to X-Forwarded-For. When a reverse proxy appends the client address to X-Forwarded-For but passes a client-supplied Forwarded header through unchanged, request.remote_ip returns an address chosen by the client, and the IP spoofing check does not raise, because it compares only Client-Ip with the forwarded addresses. An unauthenticated attacker could therefore spoof request.remote_ip, possibly bypassing IP-based access controls and rate limits keyed on the client address (including the default by: of rate_limit), and falsifying the client address in logs.

Details

The 8.1.0 change (2d084af8) switched ActionDispatch::RemoteIp from reading X-Forwarded-For directly to Rack's forwarded_for, in order to reuse Rack's port handling. Rails continues to honor Forwarded, the standard header.

In the fixed releases, when config.action_dispatch.ip_spoofing_check is enabled (the default), ActionDispatch::RemoteIp also compares the first untrusted client address in Forwarded with the first untrusted client address in X-Forwarded-For, as exact strings, and raises ActionDispatch::RemoteIp::IpSpoofAttackError when both headers are present and the addresses differ. Deployments whose proxies report the client address inconsistently between the two headers will receive this error after upgrading. See the actionpack CHANGELOG.

Affected applications

An application is affected if it meets all of these requirements:

  • Runs Rails 8.1.0 through 8.1.4 with Rack 3. Under Rack 2.2, forwarded_for reads only X-Forwarded-For.
  • Is served behind a proxy that does not remove or overwrite a client-supplied Forwarded header.
  • Relies on request.remote_ip for access control, rate limiting, or auditing.

The fix detects a spoofed Forwarded header only when the proxy also sets X-Forwarded-For. An application whose proxy passes a client-supplied Forwarded header through and sets no X-Forwarded-For remains exposed after upgrading, and should configure the proxy to remove or overwrite Forwarded, or apply the workaround below.

Mitigation

  • Upgrade to a fixed version of actionpack.
  • Configure reverse proxies to remove or overwrite any client-supplied Forwarded header.

Workarounds

Applications whose proxies set X-Forwarded-For can make Rack ignore the Forwarded header, restoring the client address resolution of Rails 8.0, by setting Rack::Request.forwarded_priority = [:x_forwarded] in an initializer. This setting is available in Rack 3.0.0 and later, and it also causes Rack to ignore Forwarded when determining the request scheme, host, and port.

Releases

The fixed releases are available at the normal locations.

Patches for those who cannot upgrade at once:

Versions affected

  • actionpack >= 8.1, < 8.1.4.1

Credit

This issue was responsibly reported by HackerOne researcher luryus.

References

5 sources
rails/rails · security/advisories/GHSA-2gff-2mmg-m73p
Security advisoryGitHub_M
rails/rails · commit 2a01a5a
PatchGitHub_M
rails/rails · repository
Source reference
rails/rails · releases/tag/v8.1.4.1
Release notesGitHub_M
rubysec/ruby-advisory-db · GHSA-2gff-2mmg-m73p.yml
Source reference

Inside the record

Evidence available

Package identity
Version evidence
Remediation guidance · not supplied
Weakness classification
Additional publishers

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-126083

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Underlying weaknesses

The source’s classification of what caused the vulnerability.

CWE-348 ↗

CWE-348: Use of Less Trusted Source

GitHub_M

Related →
Contributing organizations · 2
GitHub_M

Assigning organization

2026-11-10
CISA-ADP

Additional data publisher

2026-11-13

Timeline

All times UTC

  1. Advisory published

    Publication date supplied by the source.

  2. Source updated

    Latest modification date supplied by the source.

  3. Last imported by cve.new

    Latest catalog import, not the date we first saw this advisory.

What changed

Follow changes
  1. CVE · CVE-2026-126083

    Observed 2026-11-13T23:54:20.900Z · upstream updated 2026-11-13T16:22:49.039Z

    Prioritization updated

    before

    []

    after

    [
  {
    "source": "CISA-ADP",
    "type": "SSVC",
    "role": "CISA Coordinator",
    "timestamp": "2026-11-13T16:22:35.722742Z",
    "decisions": [
      {
        "name": "Exploitation",
        "value": "none"
      },
      {
        "name": "Automatable",
        "value": "no"
      },
      {
        "name": "Technical Impact",
        "value": "total"
      }
    ]
  }
]

Large field values are marked as truncated previews. Original source snapshots remain retained.

Showing up to 50 most recent observed changes.