How severe is CVE-2026-34826?

CVE-2026-34826 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-34826 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (30th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34826?

CVE-2026-34826 affects Rack. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34826?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-34826 have an EU (EUVD) identifier?

Yes. CVE-2026-34826 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18386.

When was CVE-2026-34826 published?

CVE-2026-34826 was published on 2026-04-02 and last updated on 2026-06-17.

CVE-2026-34826

CVE-2026-34826 is a medium-severity vulnerability in Rack with a CVSS 3.x base score of 5.3. 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-400.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (30th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-18386
Weakness: CWE-400
Affected product: Rack
Published: 2026-04-02
Last modified: 2026-06-17

Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Utils.get_byte_ranges parses the HTTP Range header without limiting the number of individual byte ranges. Although the existing fix for CVE-2024-26141 rejects ranges whose total byte coverage exceeds the file size, it does not restrict the count of ranges. An attacker can supply many small overlapping ranges such as 0-0,0-0,0-0,... to trigger disproportionate CPU, memory, I/O, and bandwidth consumption per request. This results in a denial of service condition in Rack file-serving paths that process multipart byte range responses. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

Frequently asked questions

What is CVE-2026-34826?: Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Utils.get_byte_ranges parses the HTTP Range header without limiting the number of individual byte ranges. Although the existing fix for CVE-2024-26141 rejects ranges whose total byte coverage exceeds the file size, it does not restrict the count of ranges. An attacker can supply many small overlapping ranges such as 0-0,0-0,0-0,... to trigger disproportionate CPU, memory, I/O, and bandwidth consumption per request. This results in a denial of service condition in Rack file-serving paths that process multipart byte range responses. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.
How severe is CVE-2026-34826?: CVE-2026-34826 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-34826 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (30th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34826?: CVE-2026-34826 affects Rack. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34826?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-34826 have an EU (EUVD) identifier?: Yes. CVE-2026-34826 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18386.
When was CVE-2026-34826 published?: CVE-2026-34826 was published on 2026-04-02 and last updated on 2026-06-17.

References

https://github.com/rack/rack/security/advisories/GHSA-x8cg-fq8g-mxfx

Affected products (1)

cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*

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