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Fencer Vulns
high 7.5

CVE-2026-42006 json

An attacker can cause uncontrolled memory usage with excessive bracing over IMAP.

published 2026-05-12 5 mo ago modified 2026-10-26 13 d ago also EUVD-2026-29473

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

An attacker can cause uncontrolled memory usage with excessive bracing over IMAP. The fix in CVE-2026-27857 was incomplete, only blocking one way of doing this, so there was still another way left open. In particular, the fix was for closing braces, but you could still use open braces to bypass the limit. Using excessive bracing, attacker can cause memory usage up to configured memory limit. Install fixed version, or configure vsz_limit for imap process to low value. No publicly available exploits are known.

Patch / fix

  • Red Hat Red Hat Enterprise Linux 10 1:2.3.21-19.el10_2.1
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support 1:2.3.21-16.el10_0.2
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support 1:2.2.36-8.el7_9.2
  • Red Hat Red Hat Enterprise Linux 8 1:2.3.16-8.el8_10
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 1:2.3.8-9.el8_4.2
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 1:2.3.8-9.el8_4.2
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 1:2.3.16-2.el8_6.2
  • Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On 1:2.3.16-2.el8_6.2
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service 1:2.3.16-3.el8_8.2
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 1:2.3.16-3.el8_8.2
  • Red Hat Red Hat Enterprise Linux 9 1:2.3.16-18.el9_8.1
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 1:2.3.16-8.el9_2.3
  • Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions 1:2.3.16-11.el9_4.3
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support 1:2.3.16-15.el9_6.2
  • dovecot Debian 12 1:2.3.19.1+dfsg1-2.1+deb12u6
  • dovecot Debian 13 1:2.4.1+dfsg1-6+deb13u6
  • dovecot Debian 14 1:2.4.4+dfsg1-1

debian advisories DEBIAN-CVE-2026-42006

  • dovecot Ubuntu 22.04 LTS 1:2.3.16+dfsg1-3ubuntu2.9
  • dovecot Ubuntu 24.04 LTS 1:2.3.21+dfsg1-2ubuntu6.5
  • dovecot Ubuntu 25.10 1:2.4.1+dfsg1-5ubuntu4.2
  • dovecot Ubuntu 26.04 LTS 1:2.4.2+dfsg1-3ubuntu2.1

ubuntu advisories UBUNTU-CVE-2026-42006

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

  • dovecot RHEL 8 1:2.3.16-8.el8_10
  • dovecot-mysql RHEL 8 1:2.3.16-8.el8_10
  • dovecot-pgsql RHEL 8 1:2.3.16-8.el8_10
  • dovecot-pigeonhole RHEL 8 1:2.3.16-8.el8_10
  • dovecot RHEL 10.2 1:2.3.21-19.el10_2.1
  • dovecot-mysql RHEL 10.2 1:2.3.21-19.el10_2.1
  • dovecot-pgsql RHEL 10.2 1:2.3.21-19.el10_2.1
  • dovecot-pigeonhole RHEL 10.2 1:2.3.21-19.el10_2.1

red hat advisories RHSA-2026:49513RHSA-2026:46532RHSA-2026:46380RHSA-2026:46381RHSA-2026:46379RHSA-2026:44373

  • dovecot23 SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 2.3.21.1-150200.76.1
  • dovecot24 SLES for SAP applications 16.0, SLES 16.0 2.4.4-160000.1.1
  • dovecot22 SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 2.2.31-19.37.2

suse advisories SUSE-SU-2026:4139-1SUSE-SU-2026:2645-1SUSE-SU-2026:22185-1

  • dovecot24 openSUSE Leap 16.0 2.4.4-160000.1.1
  • dovecot24 openSUSE Tumbleweed 2.4.4-1.1

opensuse advisories openSUSE-SU-2026:21109-1openSUSE-SU-2026:10766-1

  • dovecot AlmaLinux 8 1:2.3.16-8.el8_10
  • dovecot-mysql AlmaLinux 8 1:2.3.16-8.el8_10
  • dovecot-pgsql AlmaLinux 8 1:2.3.16-8.el8_10
  • dovecot-pigeonhole AlmaLinux 8 1:2.3.16-8.el8_10
  • dovecot AlmaLinux 9 1:2.3.16-18.el9_8.1
  • dovecot-mysql AlmaLinux 9 1:2.3.16-18.el9_8.1
  • dovecot-pgsql AlmaLinux 9 1:2.3.16-18.el9_8.1
  • dovecot-pigeonhole AlmaLinux 9 1:2.3.16-18.el9_8.1

almalinux advisories ALSA-2026:46532ALSA-2026:41905ALSA-2026:41988

  • dovecot Rocky Linux 8 1:2.3.16-8.el8_10
  • dovecot Rocky Linux 10 1:2.3.21-19.el10_2.1
  • dovecot Rocky Linux 9 1:2.3.16-18.el9_8.1

rocky linux advisories RLSA-2026:46532RLSA-2026:41988RLSA-2026:41905

  • dovecot Alpine 3.24, Alpine 3.23 2.4.4-r0

alpine advisories ALPINE-CVE-2026-42006

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-2026-42006 updated cvss 7.5

dovecot: Dovecot: Denial of Service via excessive IMAP bracing

  • Red Hat Enterprise Linux 6 dovecot, dovecot-mysql, dovecot-pgsql, dovecot-pigeonhole
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat CodeReady Linux Builder EUS (v.9.6) dovecot 2.3.16-15.el9_6.2
    fixed: vendor fix RHSA-2026:44355
  • Red Hat Enterprise Linux AppStream (v. 8) dovecot 2.3.16-8.el8_10, dovecot-mysql 2.3.16-8.el8_10, dovecot-pgsql 2.3.16-8.el8_10, dovecot-pigeonhole 2.3.16-8.el8_10
    fixed: vendor fix RHSA-2026:46532
  • Red Hat Enterprise Linux AppStream (v. 9) dovecot 2.3.16-18.el9_8.1, dovecot-mysql 2.3.16-18.el9_8.1, dovecot-pgsql 2.3.16-18.el9_8.1, dovecot-pigeonhole 2.3.16-18.el9_8.1
    fixed: vendor fix RHSA-2026:41905
  • Red Hat Enterprise Linux AppStream (v. 10) dovecot 2.3.21-19.el10_2.1, dovecot-mysql 2.3.21-19.el10_2.1, dovecot-pgsql 2.3.21-19.el10_2.1, dovecot-pigeonhole 2.3.21-19.el10_2.1
    fixed: vendor fix RHSA-2026:41988
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) dovecot 2.3.8-9.el8_4.2
    fixed: vendor fix RHSA-2026:46380
  • Red Hat Enterprise Linux AppStream AUS (v.8.6) dovecot 2.3.16-2.el8_6.2
    fixed: vendor fix RHSA-2026:46379
  • Red Hat Enterprise Linux AppStream E4S (v.8.8) dovecot 2.3.16-3.el8_8.2
    fixed: vendor fix RHSA-2026:46381
show 12 more
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) dovecot 2.3.16-8.el9_2.3
    fixed: vendor fix RHSA-2026:44373
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) dovecot 2.3.16-11.el9_4.3
    fixed: vendor fix RHSA-2026:44357
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) dovecot 2.3.21-16.el10_0.2
    fixed: vendor fix RHSA-2026:42091
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) dovecot 2.3.16-15.el9_6.2
    fixed: vendor fix RHSA-2026:44355
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) dovecot 2.3.8-9.el8_4.2
    fixed: vendor fix RHSA-2026:46380
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) dovecot 2.3.16-2.el8_6.2
    fixed: vendor fix RHSA-2026:46379
  • Red Hat Enterprise Linux AppStream TUS (v.8.8) dovecot 2.3.16-3.el8_8.2
    fixed: vendor fix RHSA-2026:46381
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) dovecot 2.3.16-18.el9_8.1
    fixed: vendor fix RHSA-2026:41905
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) dovecot-devel 2.3.21-19.el10_2.1, dovecot-debuginfo 2.3.21-19.el10_2.1, dovecot-debugsource 2.3.21-19.el10_2.1, dovecot-mysql-debuginfo 2.3.21-19.el10_2.1, dovecot-pgsql-debuginfo 2.3.21-19.el10_2.1, dovecot-pigeonhole-debuginfo 2.3.21-19.el10_2.1
    fixed: vendor fix RHSA-2026:41988
  • Red Hat Enterprise Linux CRB (v. 8) dovecot 2.3.16-8.el8_10
    fixed: vendor fix RHSA-2026:46532
  • Red Hat Enterprise Linux Server (v. 7 ELS) dovecot 2.2.36-8.el7_9.2
    fixed: vendor fix RHSA-2026:49513
  • Red Hat CodeReady Linux Builder EUS (v.9.6) dovecot-devel 2.3.16-15.el9_6.2, dovecot-debuginfo 2.3.16-15.el9_6.2, dovecot-debugsource 2.3.16-15.el9_6.2, dovecot-mysql-debuginfo 2.3.16-15.el9_6.2, dovecot-pgsql-debuginfo 2.3.16-15.el9_6.2, dovecot-pigeonhole-debuginfo 2.3.16-15.el9_6.2 Red Hat Enterprise Linux AppStream AUS (v.8.4) dovecot-mysql 2.3.8-9.el8_4.2, dovecot-pgsql 2.3.8-9.el8_4.2, dovecot-pigeonhole 2.3.8-9.el8_4.2 Red Hat Enterprise Linux AppStream AUS (v.8.6) dovecot-mysql 2.3.16-2.el8_6.2, dovecot-pgsql 2.3.16-2.el8_6.2, dovecot-pigeonhole 2.3.16-2.el8_6.2 Red Hat Enterprise Linux AppStream E4S (v.8.8) dovecot-mysql 2.3.16-3.el8_8.2, dovecot-pgsql 2.3.16-3.el8_8.2, dovecot-pigeonhole 2.3.16-3.el8_8.2 Red Hat Enterprise Linux AppStream E4S (v.9.2) dovecot-mysql 2.3.16-8.el9_2.3, dovecot-pgsql 2.3.16-8.el9_2.3, dovecot-pigeonhole 2.3.16-8.el9_2.3 Red Hat Enterprise Linux AppStream E4S (v.9.4) dovecot-mysql 2.3.16-11.el9_4.3, dovecot-pgsql 2.3.16-11.el9_4.3, dovecot-pigeonhole 2.3.16-11.el9_4.3
    +8 more products
    Red Hat Enterprise Linux AppStream EUS (v. 10.0) dovecot-mysql 2.3.21-16.el10_0.2, dovecot-pgsql 2.3.21-16.el10_0.2, dovecot-pigeonhole 2.3.21-16.el10_0.2 Red Hat Enterprise Linux AppStream EUS (v.9.6) dovecot-mysql 2.3.16-15.el9_6.2, dovecot-pgsql 2.3.16-15.el9_6.2, dovecot-pigeonhole 2.3.16-15.el9_6.2 Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) dovecot-mysql 2.3.8-9.el8_4.2, dovecot-pgsql 2.3.8-9.el8_4.2, dovecot-pigeonhole 2.3.8-9.el8_4.2 Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) dovecot-mysql 2.3.16-2.el8_6.2, dovecot-pgsql 2.3.16-2.el8_6.2, dovecot-pigeonhole 2.3.16-2.el8_6.2 Red Hat Enterprise Linux AppStream TUS (v.8.8) dovecot-mysql 2.3.16-3.el8_8.2, dovecot-pgsql 2.3.16-3.el8_8.2, dovecot-pigeonhole 2.3.16-3.el8_8.2 Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) dovecot-devel 2.3.21-16.el10_0.2, dovecot-debuginfo 2.3.21-16.el10_0.2, dovecot-debugsource 2.3.21-16.el10_0.2, dovecot-mysql-debuginfo 2.3.21-16.el10_0.2, dovecot-pgsql-debuginfo 2.3.21-16.el10_0.2, dovecot-pigeonhole-debuginfo 2.3.21-16.el10_0.2 Red Hat Enterprise Linux Server (v. 7 ELS) dovecot-mysql 2.2.36-8.el7_9.2, dovecot-pgsql 2.2.36-8.el7_9.2, dovecot-pigeonhole 2.2.36-8.el7_9.2 Red Hat Enterprise Linux Server Optional (v. 7 ELS) dovecot-devel 2.2.36-8.el7_9.2, dovecot-debuginfo 2.2.36-8.el7_9.2
    not affected: vulnerable code not present

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
partial
Assessed
5 mo ago

Exploit prediction

0.62% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Open-Xchange GmbH OX Dovecot Pro
  • 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 Enterprise Linux 6

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption
  • CWE-770 Allocation of Resources Without Limits or Throttling

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.