CVE-2026-27857

EUVD-2026-16567
Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remediation. No publicly available exploits are known.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
4.3 MEDIUM
NETWORK
LOW
LOW
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Base Score
CVSS 3.x
EPSS Score
Percentile: 48.46%
Affected Products (NVD)
VendorProductVersion
dovecotdovecot
𝑥
< 2.4.3
open-xchangedovecot
𝑥
< 2.3.22.1
open-xchangedovecot
3.0.0 ≤
𝑥
< 3.0.5
open-xchangedovecot
3.1.0 ≤
𝑥
< 3.1.4
𝑥
= Vulnerable software versions
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
Red HatRed Hat Enterprise Linux 10
1:2.3.21-16.el10_1.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 10
1:2.3.21-19.el10_2 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 10.0 Extended Update Support
1:2.3.21-16.el10_0.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Support
1:2.2.36-8.el7_9.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 8
1:2.3.16-7.el8_10 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
1:2.3.8-9.el8_4.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On
1:2.3.8-9.el8_4.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
1:2.3.16-2.el8_6.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 8.6 Telecommunications Update Service
1:2.3.16-2.el8_6.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 8.6 Update Services for SAP Solutions
1:2.3.16-2.el8_6.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Service
1:2.3.16-3.el8_8.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutions
1:2.3.16-3.el8_8.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 9
1:2.3.16-15.el9_7.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 9
1:2.3.16-18.el9_8 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 9.0 Update Services for SAP Solutions
1:2.3.16-3.el9_0.1 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 9.2 Update Services for SAP Solutions
1:2.3.16-8.el9_2.2 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 9.4 Extended Update Support
1:2.3.16-11.el9_4.2 ≤
𝑥
< *
ADP
Red HatRed Hat Enterprise Linux 9.6 Extended Update Support
1:2.3.16-15.el9_6.1 ≤
𝑥
< *
ADP
Debian logo
Debian Releases
Debian Product
Codename
dovecot
bookworm
1:2.3.19.1+dfsg1-2.1+deb12u6
fixed
bookworm (security)
1:2.3.19.1+dfsg1-2.1+deb12u6
fixed
bullseye
vulnerable
bullseye (security)
1:2.3.13+dfsg1-2+deb11u4
fixed
forky
1:2.4.4+dfsg1-2
fixed
sid
1:2.4.4+dfsg1-2
fixed
trixie
1:2.4.1+dfsg1-6+deb13u6
fixed
trixie (security)
1:2.4.1+dfsg1-6+deb13u6
fixed
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
dovecot
bionic
not-affected
focal
needed
jammy
Fixed 1:2.3.16+dfsg1-3ubuntu2.7
released
noble
Fixed 1:2.3.21+dfsg1-2ubuntu6.3
released
questing
Fixed 1:2.4.1+dfsg1-5ubuntu4.1
released
resolute
not-affected
trusty
not-affected
xenial
not-affected
openSUSE logo
openSUSE / SLES Releases
openSUSE Product
Release
dovecot22
suse enterprise server 12 SP3
2.2.31-19.32.1
fixed
suse enterprise server 12 SP5
2.2.31-19.32.1
fixed
dovecot22-backend-mysql
suse enterprise server 12 SP3
2.2.31-19.32.1
fixed
suse enterprise server 12 SP5
2.2.31-19.32.1
fixed
dovecot22-backend-pgsql
suse enterprise server 12 SP3
2.2.31-19.32.1
fixed
suse enterprise server 12 SP5
2.2.31-19.32.1
fixed
dovecot22-backend-sqlite
suse enterprise server 12 SP3
2.2.31-19.32.1
fixed
suse enterprise server 12 SP5
2.2.31-19.32.1
fixed
dovecot22-devel
suse enterprise server 12 SP5
2.2.31-19.32.1
fixed
Red Hat logo
Red Hat Enterprise Linux Releases
Red Hat Product
Release
dovecot
RHEL 8
1:2.3.16-7.el8_10
fixed
RHEL 8.4 AUS
1:2.3.8-9.el8_4.1
fixed
RHEL 8.6 AUS
1:2.3.16-2.el8_6.1
fixed
RHEL 8.6 E4S
1:2.3.16-2.el8_6.1
fixed
RHEL 8.6 TUS
1:2.3.16-2.el8_6.1
fixed
RHEL 8.8 E4S
1:2.3.16-3.el8_8.1
fixed
RHEL 8.8 TUS
1:2.3.16-3.el8_8.1
fixed
RHEL 9
1:2.3.16-18.el9_8
fixed
dovecot-devel
RHEL 8
1:2.3.16-7.el8_10
fixed
RHEL 9
1:2.3.16-18.el9_8
fixed
dovecot-mysql
RHEL 8
1:2.3.16-7.el8_10
fixed
RHEL 8.4 AUS
1:2.3.8-9.el8_4.1
fixed
RHEL 8.6 AUS
1:2.3.16-2.el8_6.1
fixed
RHEL 8.6 E4S
1:2.3.16-2.el8_6.1
fixed
RHEL 8.6 TUS
1:2.3.16-2.el8_6.1
fixed
RHEL 8.8 E4S
1:2.3.16-3.el8_8.1
fixed
RHEL 8.8 TUS
1:2.3.16-3.el8_8.1
fixed
RHEL 9
1:2.3.16-18.el9_8
fixed
dovecot-pgsql
RHEL 8
1:2.3.16-7.el8_10
fixed
RHEL 8.4 AUS
1:2.3.8-9.el8_4.1
fixed
RHEL 8.6 AUS
1:2.3.16-2.el8_6.1
fixed
RHEL 8.6 E4S
1:2.3.16-2.el8_6.1
fixed
RHEL 8.6 TUS
1:2.3.16-2.el8_6.1
fixed
RHEL 8.8 E4S
1:2.3.16-3.el8_8.1
fixed
RHEL 8.8 TUS
1:2.3.16-3.el8_8.1
fixed
RHEL 9
1:2.3.16-18.el9_8
fixed
dovecot-pigeonhole
RHEL 8
1:2.3.16-7.el8_10
fixed
RHEL 8.4 AUS
1:2.3.8-9.el8_4.1
fixed
RHEL 8.6 AUS
1:2.3.16-2.el8_6.1
fixed
RHEL 8.6 E4S
1:2.3.16-2.el8_6.1
fixed
RHEL 8.6 TUS
1:2.3.16-2.el8_6.1
fixed
RHEL 8.8 E4S
1:2.3.16-3.el8_8.1
fixed
RHEL 8.8 TUS
1:2.3.16-3.el8_8.1
fixed
RHEL 9
1:2.3.16-18.el9_8
fixed
Amazon Linux logo
Amazon Linux Releases
Amazon Package
Release
dovecot
Amazon Linux 2
1:2.2.36-6.amzn2.1.3
fixed
Amazon Linux 2023
1:2.3.20-1.amzn2023.0.3
fixed
dovecot-debuginfo
Amazon Linux 2
1:2.2.36-6.amzn2.1.3
fixed
Amazon Linux 2023
1:2.3.20-1.amzn2023.0.3
fixed
dovecot-debugsource
Amazon Linux 2023
1:2.3.20-1.amzn2023.0.3
fixed
dovecot-devel
Amazon Linux 2
1:2.2.36-6.amzn2.1.3
fixed
Amazon Linux 2023
1:2.3.20-1.amzn2023.0.3
fixed
dovecot-mysql
Amazon Linux 2
1:2.2.36-6.amzn2.1.3
fixed
Amazon Linux 2023
1:2.3.20-1.amzn2023.0.3
fixed
dovecot-mysql-debuginfo
Amazon Linux 2023
1:2.3.20-1.amzn2023.0.3
fixed
dovecot-pgsql
Amazon Linux 2
1:2.2.36-6.amzn2.1.3
fixed
Amazon Linux 2023
1:2.3.20-1.amzn2023.0.3
fixed
dovecot-pgsql-debuginfo
Amazon Linux 2023
1:2.3.20-1.amzn2023.0.3
fixed
dovecot-pigeonhole
Amazon Linux 2
1:2.2.36-6.amzn2.1.3
fixed
Amazon Linux 2023
1:2.3.20-1.amzn2023.0.3
fixed
dovecot-pigeonhole-debuginfo
Amazon Linux 2023
1:2.3.20-1.amzn2023.0.3
fixed
Common Weakness Enumeration
References
https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json
https://access.redhat.com/errata/RHSA-2026:13498
https://access.redhat.com/errata/RHSA-2026:13830
https://access.redhat.com/errata/RHSA-2026:13857
https://access.redhat.com/errata/RHSA-2026:17602
https://access.redhat.com/errata/RHSA-2026:17625
https://access.redhat.com/errata/RHSA-2026:17626
https://access.redhat.com/errata/RHSA-2026:17628
https://access.redhat.com/errata/RHSA-2026:17630
https://access.redhat.com/errata/RHSA-2026:18053
https://access.redhat.com/errata/RHSA-2026:19149
https://access.redhat.com/errata/RHSA-2026:19364
https://access.redhat.com/errata/RHSA-2026:19453
https://access.redhat.com/errata/RHSA-2026:19455
https://access.redhat.com/errata/RHSA-2026:26564
https://access.redhat.com/security/cve/CVE-2026-27857
https://bugzilla.redhat.com/show_bug.cgi?id=2452179
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27857.json