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CVE-2026-125110

Rack: Rack::Static header_rules bypass via dot-segment normalization mismatch

Products / packages rack

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Severity and exploitation

Not in CISA KEVSource: MODERATE

KEV coverage does not rule out exploitation.

KEV checked 15/11/2026, 02:00:33 UTC
OSV · CVSS:3.1 · 5.3
Assessment vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
GitHub_M · CVSS:3.1 · 5.3
Assessment vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
The headline uses the highest imported catalog score. Assessments can differ by source and CVSS version.

Severity

medium5.3

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

Rack::Static normalizes the request path with Utils.clean_path_info when deciding which file to serve, but matches header_rules against a path that is only URL-decoded. A request containing dot segments, raw or percent-encoded, is served the normalized target file while the header rules for that file's location are not applied.

Source excerpt · OSV

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.

rack · GitHub_M

rack

3 ranges
GitHub_M version evidence

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

affected

< 2.2.25

>= 3.0, < 3.1.23

>= 3.2, < 3.2.8

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.

rack RubyGems
Affected range Recorded fix
Earlier releases before 2.2.25Ecosystem versions2.2.25
From 3.0.0 before 3.1.23Ecosystem versions3.1.23
From 3.2.0 before 3.2.8Ecosystem versions3.2.8

Version evidence: OSV · GHSA-wvg4-6p58-3gh3

View original version evidence (179 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

Summary

Rack::Static normalizes the request path with Utils.clean_path_info when deciding which file to serve, but matches header_rules against a path that is only URL-decoded. A request containing dot segments, raw or percent-encoded, is served the normalized target file while the header rules for that file's location are not applied.

This allows an attacker to receive a protected static file without the security headers configured for it.

Details

Rack::Static#call computes the served path as Utils.clean_path_info(Utils.unescape_path(path)). Rack::Static#applicable_rules applies only Utils.unescape_path before testing string and regular expression rules. A request for /assets/../uploads/file.html or /assets/..%2fuploads/file.html is served as uploads/file.html, but the decoded path /assets/../uploads/file.html does not start with uploads, so a rule scoped to that directory never matches.

The fix for CVE-2026-34786 (GHSA-q4qf-9j86-f5mh) added URL decoding to rule matching but did not add dot segment normalization, so versions that include that fix remain affected.

Impact

Applications that use Rack::Static header_rules to attach security-relevant headers to particular paths or file types are affected. An unauthenticated attacker who knows the path of a protected file can request it through a dot segment path and receive it without those headers, for example without Content-Disposition: attachment or a restrictive Content-Security-Policy that prevents uploaded HTML from rendering inline. The file itself is served unchanged. Applications that do not use path-specific header_rules are not affected.

Mitigation

  • Update to a patched version of Rack in which header_rules are matched against the same normalized path used to serve the file.
  • Reject requests containing dot segments at a reverse proxy or application boundary.
  • Do not rely solely on Rack::Static header_rules to prevent inline rendering of untrusted uploads; serve them from a separate origin.

Credit

  • Reporter and Remediation developer

References

7 sources
rack/rack · security/advisories/GHSA-wvg4-6p58-3gh3
Security advisoryGitHub_M
nvd.nist.gov/vuln/detail/CVE-2026-125110
Security advisory
rack/rack · commit 18a07fe
PatchGitHub_M
rack/rack · commit 9d7f194
PatchGitHub_M
rack/rack · commit e88097c
PatchGitHub_M
rack/rack · repository
Source reference
View 1 more references
rubysec/ruby-advisory-db · GHSA-wvg4-6p58-3gh3.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-2026-125110

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-180 ↗

CWE-180: Incorrect Behavior Order: Validate Before Canonicalize

GitHub_M

Related →
Contributing organizations · 2
GitHub_M

Assigning organization

2026-11-09
CISA-ADP

Additional data publisher

2026-11-14

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-2026-125110

    Observed 2026-11-14T03:20:52.178Z · upstream updated 2026-11-14T02:25:26.839Z

    Prioritization updated

    before

    []

    after

    [
  {
    "source": "CISA-ADP",
    "type": "SSVC",
    "role": "CISA Coordinator",
    "timestamp": "2026-11-14T02:25:17.811506Z",
    "decisions": [
      {
        "name": "Exploitation",
        "value": "none"
      },
      {
        "name": "Automatable",
        "value": "yes"
      },
      {
        "name": "Technical Impact",
        "value": "partial"
      }
    ]
  }
]

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

Showing up to 50 most recent observed changes.