How severe is CVE-2026-42256?

CVE-2026-42256 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-42256 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-42256?

CVE-2026-42256 affects Ruby-lang Net. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-42256?

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

Does CVE-2026-42256 have an EU (EUVD) identifier?

Yes. CVE-2026-42256 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28925.

When was CVE-2026-42256 published?

CVE-2026-42256 was published on 2026-05-09 and last updated on 2026-06-17.

CVE-2026-42256

CVE-2026-42256 is a medium-severity vulnerability in Ruby-lang Net with a CVSS 3.x base score of 6.5. 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-770.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v4: 6.0
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-28925
Weakness: CWE-770
Affected product: Ruby-lang Net
Published: 2026-05-09
Last modified: 2026-06-17

Description

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. From versions 0.4.0 to before 0.4.24, 0.5.0 to before 0.5.14, and 0.6.0 to before 0.6.4, when authenticating a connection with SCRAM-SHA1 or SCRAM-SHA256, a hostile server can perform a computational denial-of-service attack on the client process by sending a big iteration count value. This issue has been patched in versions 0.4.24, 0.5.14, and 0.6.4.

Frequently asked questions

What is CVE-2026-42256?: Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. From versions 0.4.0 to before 0.4.24, 0.5.0 to before 0.5.14, and 0.6.0 to before 0.6.4, when authenticating a connection with SCRAM-SHA1 or SCRAM-SHA256, a hostile server can perform a computational denial-of-service attack on the client process by sending a big iteration count value. This issue has been patched in versions 0.4.24, 0.5.14, and 0.6.4.
How severe is CVE-2026-42256?: CVE-2026-42256 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-42256 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42256?: CVE-2026-42256 affects Ruby-lang Net. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-42256?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-42256 have an EU (EUVD) identifier?: Yes. CVE-2026-42256 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28925.
When was CVE-2026-42256 published?: CVE-2026-42256 was published on 2026-05-09 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*

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