CVE-2026-26962
CVE-2026-26962 is a medium-severity vulnerability in Rack with a CVSS 3.x base score of 4.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-93.
Key facts
- Severity: Medium (CVSS 3.x base score 4.8)
- EPSS exploit prediction: 0% (15th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-18417
- Weakness: CWE-93
- Affected product: Rack
- Published:
- Last modified:
Description
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.
Frequently asked questions
- What is CVE-2026-26962?
- 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.
- How severe is CVE-2026-26962?
- CVE-2026-26962 has a CVSS 3.x base score of 4.8, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
- Is CVE-2026-26962 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-26962?
- CVE-2026-26962 affects Rack. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-26962?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- Does CVE-2026-26962 have an EU (EUVD) identifier?
- Yes. CVE-2026-26962 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18417.
- When was CVE-2026-26962 published?
- CVE-2026-26962 was published on 2026-04-02 and last updated on 2026-07-24.
References
Affected products (1)
- cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
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