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NVD / CVE Program· CNA GitHub_M

CVE-2026-26962: Rack: Header injection in multipart requests

Noroxi assessment

Priority: Monitor (action score 26/100)

  • 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: 0.23% (FIRST EPSS).
  • 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: rack rack 3.2.6.

Low priority for now. Upgrade to rack rack 3.2.6 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

Rack is a modular Ruby web server interface. From version 3.2.0 to before version 3.2.6, Rack::Multipart::Parser unfolds folded multipart part headers incorrectly. When a multipart header contains an obs-fold sequence, Rack preserves the embedded CRLF in parsed parameter values such as filename or name instead of removing the folded line break during unfolding. As a result, applications that later reuse those parsed values in HTTP response headers may be vulnerable to downstream header injection or response splitting. This issue has been patched in version 3.2.6.

MediumCVSS 6.5 · v3.1—No exploit Fix available
Published
Apr 2, 2026
Updated
Jul 24, 2026
EPSS
0.2% · 14th percentile

Report tools

JSON

Action score

26

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
6.5
CNA · GitHub_M
4.8
1.7 point gap

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

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-2026-26962

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.

VendorProduct
rackrack

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • rack rack3.2.0 and later · before 3.2.6

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.

  • rack rack

    • >= 3.2.0, < 3.2.6affected

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:13ruby-rackbefore 3.1.20-0+deb13u23.1.20-0+deb13u2
Debian:14ruby-rackbefore 3.2.6-23.2.6-2
openSUSE:Leap 16.0rmt-serverbefore 3.1.0-160000.1.13.1.0-160000.1.1
RubyGemsrackfrom 3.2.0 · before 3.2.63.2.6
SUSE:Linux Enterprise Module for Public Cloud 15 SP5rmt-serverbefore 2.27-150500.3.47.12.27-150500.3.47.1
SUSE:Linux Enterprise Server 16.0rmt-serverbefore 3.1.0-160000.1.13.1.0-160000.1.1

Same product

rack: all records

Other highest-scoring records for the same primary product.

  • CVE-2024-25126Rack ReDos in content type parsing (2nd degree polynomial)
    41Plan
  • CVE-2024-26146Possible Denial of Service Vulnerability in Rack Header Parsing
    31Monitor
  • CVE-2023-27530A DoS vulnerability exists in Rack <v3.0.4.2, <v2.2.6.3, <v2.1.4.3 and <v2.0.9.3 within in the Multipart MIME parsing code in which could al
    31Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-34830Apr 2, 2026 · Rack: Rack::Sendfile regex injection via HTTP_X_ACCEL_MAPPING header allows arbitrary file reads through nginx
    30Monitor
  • ← EarlierCVE-2026-34831Apr 2, 2026 · Rack: Content-Length mismatch in Rack::Files error responses
    26Monitor
  • Later →CVE-2026-32762Apr 2, 2026 · Rack: Forwarded Header semicolon injection enables Host and Scheme spoofing
    26Monitor

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
rack rack3.2.6 · descriptionVendor (CNA)
debian:ruby-rack3.1.20-0+deb13u2 · Debian:13Package registry (OSV)
opensuse:rmt-server3.1.0-160000.1.1 · openSUSE:Leap 16.0Package registry (OSV)
RubyGems:rack3.2.6Package registry (OSV)
suse:rmt-server3.1.0-160000.1.1 · SUSE:Linux Enterprise Server 16.0Package 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.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

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

No commit or PR link among the references.

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.

  • CVE-2025-27111394 days apartEscape Sequence Injection vulnerability in Rack lead to Possible Log Injection
    27Monitor
  • CVE-2025-25184414 days apartPossible Log Injection in Rack::CommonLogger
    22Monitor

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

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

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
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-93 · Improper Neutralization of CRLF Sequences ('CRLF Injection')

CVSS vector

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

nvd-primary

Attack context

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

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

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

References

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

All records