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Fencer Vulns
high 7.4

CVE-2026-42246 json

net-imap vulnerable to STARTTLS stripping via invalid response timing

published 2026-05-04 6 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-28924 , GHSA-vcgp-9326-pqcp

cvss
7.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4, a man-in-the-middle attacker can cause Net::IMAP#starttls to return "successfully", without starting TLS. This issue has been patched in versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4.

Patch / fix

  • rubygems net-imap 0.3.10, 0.4.24, 0.5.14, 0.6.4
  • Red Hat Red Hat Enterprise Linux 10 0:3.3.10-13.el10_2, 0:4.0.3-35.el10_2
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support 0:3.3.10-11.el10_0.2
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:2.0.0.648-39.el7_9.1
  • Red Hat Red Hat Enterprise Linux 8 8100020260615131010.489197e6, 8100020260615131019.489197e6
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 8040020260630124058.522a0ee4
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 8040020260630124058.522a0ee4
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 8060020260630123825.ad008a3a
  • Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On 8060020260630123825.ad008a3a
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service 8080020260625114827.63b34585
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 8080020260625114827.63b34585
  • Red Hat Red Hat Enterprise Linux 9 0:3.0.7-167.el9_8, 9080020260615131001.9, 9080020260619130154.9
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 0:3.0.4-161.el9_2.3
  • Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions 0:3.0.7-162.el9_4.3, 9040020260630065449.9
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support 0:3.0.7-165.el9_6.1, 9060020260630075016.9
  • Red Hat Red Hat Hardened Images 3.3.10-23.2.hum1, 3.4.8-31.2.hum1, 3.4.10-31.hum1, 4.0.0-33.4.hum1
  • ruby3.3 Debian 13 3.3.13-0+deb13u1

debian advisories DEBIAN-CVE-2026-42246

  • ruby3.0 Ubuntu 22.04 LTS 3.0.2-7ubuntu2.13
  • ruby3.2 Ubuntu 24.04 LTS 3.2.3-1ubuntu0.24.04.8
  • ruby3.3 Ubuntu 26.04 LTS 3.3.8-2ubuntu3.1
  • ruby2.3 Ubuntu Pro 16.04 LTS 2.3.1-2~ubuntu16.04.16+esm14
  • ruby2.5 Ubuntu Pro 18.04 LTS 2.5.1-1ubuntu1.16+esm8
  • ruby2.7 Ubuntu Pro 20.04 LTS 2.7.0-5ubuntu1.18+esm5

ubuntu advisories UBUNTU-CVE-2026-42246

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • ruby3.4 hummingbird 1 3.4.10-31.hum1
  • ruby3.4-libs hummingbird 1 3.4.10-31.hum1
  • rubygem3.4-irb hummingbird 1 1.14.3-31.hum1
  • rubygem3.4-rbs hummingbird 1 3.8.0-31.hum1
  • rubygem3.4-rss hummingbird 1 0.3.1-31.hum1
  • rubygem3.4-json hummingbird 1 2.9.1-31.hum1
  • rubygem3.4-racc hummingbird 1 1.8.1-31.hum1
  • rubygem3.4-rake hummingbird 1 13.2.1-31.hum1

red hat advisories RHSA-2026:38694RHSA-2026:37397RHSA-2026:37238RHSA-2026:36099RHSA-2026:35895RHSA-2026:35867

  • hawk2 SLE High Availability Extension 16.0, SLES for SAP applications 16.0 2.7.2+git.1788518533.7d4dadd6-160000.1.1

suse advisories SUSE-SU-2026:24195-1SUSE-SU-2026:24250-1

  • hawk2 openSUSE Tumbleweed 2.7.2+git.1792148770.648dcddb-1.1
  • hawk2 openSUSE Leap 16.0 2.7.2+git.1788518533.7d4dadd6-160000.1.1

opensuse advisories openSUSE-SU-2026:12153-1openSUSE-SU-2026:22068-1

  • ruby AlmaLinux 9 3.0.7-167.el9_8
  • rubygems AlmaLinux 9 3.2.33-167.el9_8
  • ruby-libs AlmaLinux 9 3.0.7-167.el9_8
  • rubygem-irb AlmaLinux 9 1.3.5-167.el9_8
  • rubygem-rbs AlmaLinux 9 1.4.0-167.el9_8
  • rubygem-rss AlmaLinux 9 0.2.9-167.el9_8
  • rubygem-json AlmaLinux 9 2.5.1-167.el9_8
  • rubygem-rake AlmaLinux 9 13.0.3-167.el9_8

almalinux advisories ALSA-2026:33512ALSA-2026:33514ALSA-2026:33515ALSA-2026:33540ALSA-2026:33565ALSA-2026:33576

  • ruby Rocky Linux 9 3.0.7-167.el9_8
  • ruby4.0 Rocky Linux 10 4.0.3-35.el10_2
  • ruby Rocky Linux 10 3.3.10-13.el10_2
  • rubygem-pg Rocky Linux 9 1.5.4-2.module+el9.7.0+40188+314ad260.0.1
  • rubygem-mysql2 Rocky Linux 9 0.5.5-3.module+el9.7.0+40032+36e56d0d
  • rubygem-pg Rocky Linux 9 1.6.3-1.module+el9.8.0+40094+ce01217c
  • rubygem-mysql2 Rocky Linux 9 0.5.7-1.module+el9.8.0+40094+ce01217c
  • rubygem-pg Rocky Linux 8 1.0.0-3.module+el8.9.0+1536+5f79634e

rocky linux advisories RLSA-2026:33512RLSA-2026:33540RLSA-2026:33565RLSA-2026:33576RLSA-2026:33577RLSA-2026:33514

  • ruby-net-imap Alpine 3.21 0.4.25-r0

alpine advisories ALPINE-CVE-2026-42246

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-42246 updated cvss 7.4

net-imap: ruby: Net::IMAP: Information disclosure via man-in-the-middle attack bypassing TLS

  • Red Hat Enterprise Linux 6 ruby, ruby-ri, ruby-irb, ruby-libs, ruby-rdoc, ruby-tcltk
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat CodeReady Linux Builder EUS (v.9.6) ruby-doc 3.0.7-165.el9_6.1
    fixed: vendor fix RHSA-2026:33462
  • Red Hat Enterprise Linux AppStream (v. 8) ruby 3.3.10-7.module+el8.10.0+24407+4a33a056, ruby 2.5.9-115.module+el8.10.0+24408+7ffaaa88, rubygem-pg 1.0.0-3.module+el8.9.0+19193+435404ae, rubygems 3.5.22-7.module+el8.10.0+24407+4a33a056, ruby-irb 2.5.9-115.module+el8.10.0+24408+7ffaaa88, ruby-libs 3.3.10-7.module+el8.10.0+24407+4a33a056, +41 more
    fixed: vendor fix RHSA-2026:33514
  • Red Hat Enterprise Linux AppStream (v. 9) ruby 3.0.7-167.el9_8, ruby-libs 3.0.7-167.el9_8, rubygems 3.2.33-167.el9_8, rubygem-irb 1.3.5-167.el9_8, rubygem-rbs 1.4.0-167.el9_8, rubygem-rss 0.2.9-167.el9_8, +59 more
    fixed: vendor fix RHSA-2026:33512
  • Red Hat Enterprise Linux AppStream (v. 10) ruby 3.3.10-13.el10_2, ruby4.0 4.0.3-35.el10_2, rubygems 3.5.22-13.el10_2, ruby-libs 3.3.10-13.el10_2, rubygem-rbs 3.4.0-13.el10_2, rubygem-rss 0.3.1-13.el10_2, +18 more
    fixed: vendor fix RHSA-2026:33565
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) ruby 2.5.9-109.module+el8.4.0+24479+aaeed2c5, rubygem-pg 1.0.0-2.module+el8.1.0+3656+f80bfa1d, ruby-irb 2.5.9-109.module+el8.4.0+24479+aaeed2c5, ruby-libs 2.5.9-109.module+el8.4.0+24479+aaeed2c5, rubygem-abrt 0.3.0-4.module+el8.1.0+3656+f80bfa1d, rubygem-bson 4.3.0-2.module+el8.1.0+3656+f80bfa1d, +17 more
    fixed: vendor fix RHSA-2026:35866
  • Red Hat Enterprise Linux AppStream AUS (v.8.6) ruby 2.5.9-112.module+el8.6.0+24478+6e23d6ba, rubygem-pg 1.0.0-2.module+el8.1.0+3656+f80bfa1d, ruby-irb 2.5.9-112.module+el8.6.0+24478+6e23d6ba, ruby-libs 2.5.9-112.module+el8.6.0+24478+6e23d6ba, rubygem-abrt 0.3.0-4.module+el8.1.0+3656+f80bfa1d, rubygem-bson 4.3.0-2.module+el8.1.0+3656+f80bfa1d, +17 more
    fixed: vendor fix RHSA-2026:35867
  • Red Hat Enterprise Linux AppStream E4S (v.8.8) ruby 2.5.9-112.module+el8.8.0+24452+e70e99ef, rubygem-pg 1.0.0-2.module+el8.1.0+3656+f80bfa1d, ruby-irb 2.5.9-112.module+el8.8.0+24452+e70e99ef, ruby-libs 2.5.9-112.module+el8.8.0+24452+e70e99ef, rubygem-abrt 0.3.0-4.module+el8.1.0+3656+f80bfa1d, rubygem-bson 4.3.0-2.module+el8.1.0+3656+f80bfa1d, +17 more
    fixed: vendor fix RHSA-2026:34076
show 14 more
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) ruby 3.0.4-161.el9_2.3, ruby-libs 3.0.4-161.el9_2.3, rubygems 3.2.33-161.el9_2.3, rubygem-irb 1.3.5-161.el9_2.3, rubygem-rbs 1.4.0-161.el9_2.3, rubygem-rss 0.2.9-161.el9_2.3, +13 more
    fixed: vendor fix RHSA-2026:35834
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) ruby 3.0.7-162.el9_4.3, ruby-libs 3.0.7-162.el9_4.3, rubygems 3.2.33-162.el9_4.3, rubygem-irb 1.3.5-162.el9_4.3, rubygem-rbs 1.4.0-162.el9_4.3, rubygem-rss 0.2.9-162.el9_4.3, +36 more
    fixed: vendor fix RHSA-2026:33630
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) ruby 3.3.10-11.el10_0.2, rubygems 3.5.22-11.el10_0.2, ruby-libs 3.3.10-11.el10_0.2, rubygem-rbs 3.4.0-11.el10_0.2, rubygem-rss 0.3.1-11.el10_0.2, rubygem-irb 1.13.1-11.el10_0.2, +15 more
    fixed: vendor fix RHSA-2026:35895
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) ruby 3.0.7-165.el9_6.1, ruby-libs 3.0.7-165.el9_6.1, rubygems 3.2.33-165.el9_6.1, rubygem-irb 1.3.5-165.el9_6.1, rubygem-rbs 1.4.0-165.el9_6.1, rubygem-rss 0.2.9-165.el9_6.1, +36 more
    fixed: vendor fix RHSA-2026:33462
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) ruby 2.5.9-109.module+el8.4.0+24479+aaeed2c5, rubygem-pg 1.0.0-2.module+el8.1.0+3656+f80bfa1d, ruby-irb 2.5.9-109.module+el8.4.0+24479+aaeed2c5, ruby-libs 2.5.9-109.module+el8.4.0+24479+aaeed2c5, rubygem-abrt 0.3.0-4.module+el8.1.0+3656+f80bfa1d, rubygem-bson 4.3.0-2.module+el8.1.0+3656+f80bfa1d, +17 more
    fixed: vendor fix RHSA-2026:35866
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) ruby 2.5.9-112.module+el8.6.0+24478+6e23d6ba, rubygem-pg 1.0.0-2.module+el8.1.0+3656+f80bfa1d, ruby-irb 2.5.9-112.module+el8.6.0+24478+6e23d6ba, ruby-libs 2.5.9-112.module+el8.6.0+24478+6e23d6ba, rubygem-abrt 0.3.0-4.module+el8.1.0+3656+f80bfa1d, rubygem-bson 4.3.0-2.module+el8.1.0+3656+f80bfa1d, +17 more
    fixed: vendor fix RHSA-2026:35867
  • Red Hat Enterprise Linux AppStream TUS (v.8.8) ruby 2.5.9-112.module+el8.8.0+24452+e70e99ef, rubygem-pg 1.0.0-2.module+el8.1.0+3656+f80bfa1d, ruby-irb 2.5.9-112.module+el8.8.0+24452+e70e99ef, ruby-libs 2.5.9-112.module+el8.8.0+24452+e70e99ef, rubygem-abrt 0.3.0-4.module+el8.1.0+3656+f80bfa1d, rubygem-bson 4.3.0-2.module+el8.1.0+3656+f80bfa1d, +17 more
    fixed: vendor fix RHSA-2026:34076
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) ruby-doc 3.0.7-167.el9_8
    fixed: vendor fix RHSA-2026:33512
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) ruby-doc 3.3.10-13.el10_2, ruby4.0-doc 4.0.3-35.el10_2
    fixed: vendor fix RHSA-2026:33565
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) ruby-doc 3.3.10-11.el10_0.2
    fixed: vendor fix RHSA-2026:35895
  • Red Hat Enterprise Linux Server (v. 7 ELS) ruby 2.0.0.648-39.el7_9.1, rubygems 2.0.14.1-39.el7_9.1, ruby-irb 2.0.0.648-39.el7_9.1, rubygem-json 1.7.7-39.el7_9.1, rubygem-rdoc 4.0.0-39.el7_9.1, ruby-libs 2.0.0.648-39.el7_9.1, +3 more Red Hat Enterprise Linux Server Optional (v. 7 ELS) rubygem-rake 0.9.6-39.el7_9.1, ruby-tcltk 2.0.0.648-39.el7_9.1, rubygem-minitest 4.3.2-39.el7_9.1
    fixed: vendor fix RHSA-2026:37397
  • Red Hat Hardened Images ruby3.4 3.4.10-31.hum1, ruby3.4 3.4.8-31.2.hum1, ruby4.0 4.0.0-33.4.hum1, ruby3.3 3.3.10-23.2.hum1, ruby3.4-libs 3.4.10-31.hum1, ruby3.4-libs 3.4.8-31.2.hum1, +78 more
    fixed: vendor fix RHSA-2026:33721
  • Red Hat 3scale API Management Platform 2 3scale-amp21/zync, 3scale-amp22/zync, 3scale-amp21/system, 3scale-amp22/system, 3scale-amp2/zync-rhel8, 3scale-amp2/zync-rhel9, +3 more
    not affected: component not present
  • Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    not affected: vulnerable code not in execute path

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
5 mo ago

Exploit prediction

0.31% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 7.6 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CISA ADP 3.1 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA 4.0 7.6 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA 3.1 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
rubygems net-imap
>=0.6.0, <0.6.4
>=0.5.0, <0.5.14
>=0.4.0, <0.4.24
<0.3.10
0.6.4
0.5.14
0.4.24
0.3.10

Affected products

  • ruby net-imap
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support
  • Red Hat Red Hat Hardened Images
  • Red Hat Red Hat 3scale API Management Platform 2
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat OpenShift Container Platform 4

Classification

Weakness
  • CWE-392 Missing Report of Error Condition
  • CWE-393 Return of Wrong Status Code
  • CWE-754 Improper Check for Unusual or Exceptional Conditions
  • CWE-636 Not Failing Securely
  • CWE-841 Improper Enforcement of Behavioral Workflow
  • CWE-325 Missing Cryptographic Step

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.