Evidence used
- No CISA KEV confirmation is currently recorded.
- EPSS is 0.52% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-42256High confidence
net-imap: Denial of service via high iteration count for `SCRAM-*` authentication
ruby · net-imap
Official source article: GitHub GHSA-87PF-FPWV-P7M7 ↗. Check the applicable product and release in the original source.
6.0MediumCVSS 4.0
Patch only the product branches with a verified fix
Fix availability varies by productMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 4 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:Medium, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs ruby net-imap and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Remediation availability differs by product scope
Verified remediation exists for at least one product or source, but 4 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Debian Security Tracker: 4 affected package states with no published fix
Distribution package intelligence
4 package statesRelease-specific package status
Debian findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
Package result overrides the generic status
BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 4 affected package states shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
| Distribution release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | ruby3.3 | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian bookwormbookworm · source | ruby3.1 | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian forkyforky · source | ruby3.3 | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian sidsid · source | ruby3.3 | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
Open-source package ranges6 source-attributed ranges
These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.
| Ecosystem and package | Affected range | First fixed version | Evidence |
|---|---|---|---|
| RubyGemsnet-imap | ECOSYSTEM: introduced 0.6.0; fixed 0.6.4 | 0.6.4 | OSV record ↗aggregator derived · 10 Sep 2026 |
| RubyGemsnet-imap | ECOSYSTEM: introduced 0.5.0; fixed 0.5.14 | 0.5.14 | OSV record ↗aggregator derived · 10 Sep 2026 |
| RubyGemsnet-imap | ECOSYSTEM: introduced 0.4.0; fixed 0.4.24 | 0.4.24 | OSV record ↗aggregator derived · 10 Sep 2026 |
| rubygemsnet-imap | >= 0.6.0, <= 0.6.3 | 0.6.4 | GitHub advisory ↗upstream repository advisory · 14 May 2026 |
| rubygemsnet-imap | >= 0.5.0, <= 0.5.13 | 0.5.14 | GitHub advisory ↗upstream repository advisory · 14 May 2026 |
| rubygemsnet-imap | >= 0.4.0, <= 0.4.23 | 0.4.24 | GitHub advisory ↗upstream repository advisory · 14 May 2026 |
Direct vendor intelligence
2 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2026-42256 · CSAF 2.0 · revision 10 · interimSUSE Product Security TeamCVE-2026-42256
The vendor explicitly identifies these products as affected by this CVE.
- ruby as component of SUSE Linux Enterprise Server 16.0
- ruby-devel as component of SUSE Linux Enterprise Server 16.0
- ruby as component of SUSE Linux Enterprise Server for SAP applications 16.0
- ruby-devel as component of SUSE Linux Enterprise Server for SAP applications 16.0
- ruby as component of openSUSE Leap 16.0
- Summary
- 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.
- Remediation
- To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
CVE-2026-42256 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication
The vendor explicitly identifies these products as affected by this CVE.
- 3scale-amp2/system-rhel7 as a component of Red Hat 3scale API Management Platform 2
- 3scale-amp2/system-rhel8 as a component of Red Hat 3scale API Management Platform 2
- 3scale-amp2/system-rhel9 as a component of Red Hat 3scale API Management Platform 2
- 3scale-amp2/zync-rhel8 as a component of Red Hat 3scale API Management Platform 2
- 3scale-amp2/zync-rhel9 as a component of Red Hat 3scale API Management Platform 2
- 3scale-amp21/system as a component of Red Hat 3scale API Management Platform 2
- 3scale-amp21/zync as a component of Red Hat 3scale API Management Platform 2
- 3scale-amp22/system as a component of Red Hat 3scale API Management Platform 2
- 3scale-amp22/zync as a component of Red Hat 3scale API Management Platform 2
- Summary
- A flaw was found in Net::IMAP, a Ruby library for Internet Message Access Protocol (IMAP) client functionality. A hostile server can exploit this vulnerability during SCRAM-SHA1 or SCRAM-SHA256 (Salted Challenge Response Authentication Mechanism - Secure Hash Algorithm 1 or 256) authentication by sending an excessively large iteration count value. This can lead to a computational denial-of-service attack, causing the client process to become unresponsive.
- Remediation
- For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 4 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
Fix availability varies by product01
What, why and how
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.
What
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.
Why
The product uses a non-blocking model that relies on a single threaded process for features such as scalability, but it contains code that can block when it is invoked.
How
An attacker operating through a network path may attempt exploitation when the stated preconditions are met. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
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.
Why
The product uses a non-blocking model that relies on a single threaded process for features such as scalability, but it contains code that can block when it is invoked.
How
An attacker operating through a network path may attempt exploitation when the stated preconditions are met. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Use of Blocking Code in Single-threaded, Non-blocking Context → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- Passive interaction required
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Not a CVSS 4.0 base metric
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-1322 ↗
CWE-1322: Use of Blocking Code in Single-threaded, Non-blocking Context. The product uses a non-blocking model that relies on a single threaded process for features such as scalability, but it contains code that can block when it is invoked.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NCommon Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATPresentAttack requirements: A particular deployment or execution condition must be present.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIPassiveUser interaction: A user must unknowingly interact with the vulnerable system.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VINoneVulnerable-system integrity: No direct loss is represented by this metric.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Fix availability varies by product
- Affected
- ruby as component of SUSE Linux Enterprise Server 16.0
- ruby-devel as component of SUSE Linux Enterprise Server 16.0
- ruby as component of SUSE Linux Enterprise Server for SAP applications 16.0
- ruby-devel as component of SUSE Linux Enterprise Server for SAP applications 16.0
- ruby as component of openSUSE Leap 16.0
- Action
- Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
- Workaround
- A mitigation or workaround reference is available from the source linked below; validate it against the affected product and version.
04
Evidence and provenance
Published 9 May 2026 · Last source change 11 May 2026, 17:04 UTC · CWE-1322 · Use of Blocking Code in Single-threaded, Non-blocking Context
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2026-28925
Product sourceVendor CSAF · SUSE Product Security Team
Remediation sourceVendor CSAF · SUSE Product Security Team
CWE sourceCNA
NVD statusNVD enriched
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- >= 0.4.0, < 0.4.24; >= 0.5.0, < 0.5.14; >= 0.6.0, < 0.6.4 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
- After
- >= 0.4.0, < 0.4.24; >= 0.5.0, < 0.5.14; >= 0.6.0, < 0.6.4 · Fixed: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2026-28925↗Vendor CSAF · SUSE Product Security Team↗Red Hat Product Security security advisory↗CVE authority or vendor reference · GitHub GHSA-87PF-FPWV-P7M7↗Patch or update reference↗Patch or update reference↗Patch or update reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.