CVE-2026-27857

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.

Published: 2026-03-27 Last update: 2026-04-30 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-27857 is rated Low Risk (18.6/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.02%). Low composite risk—no urgent action required; patch on your normal maintenance cycle and revisit priority if CVSS or EPSS increases.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-27857

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-30 0.05% 0.02% -0.03%
2 2026-04-28 0.04% 0.05% +0.01%
3 2026-03-27 — 0.04% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-27857

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.8 1.4 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2026-27857

OS Trackers for CVE-2026-27857

vendor priority summary link
alpine — CVE-2026-27857: 1 source package rows (dovecot); 2 state rows across 2 repos (3.23-main, edge-main); fixed 2, open 0. https://security.alpinelinux.org/vuln/CVE-2026-27857
debian not yet assigned CVE-2026-27857 not yet assigned priority: Debian including 1 source packages (dovecot), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2026-27857
redhat high — https://access.redhat.com/security/cve/CVE-2026-27857
suse medium CVE-2026-27857 severity moderate: SUSE including 9 source package names (dovecot, dovecot24-2.4.3-1.1, …), 29 product×package rows across 22 product lines (SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS, SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS, … (22 product lines)): Known Not Affected 21, Fixed 8. https://www.suse.com/security/cve/CVE-2026-27857/
ubuntu medium CVE-2026-27857 medium priority: Ubuntu including 1 source packages (dovecot), 8 status rows across 8 suites (bionic, focal, jammy, noble, questing, trusty, upstream, xenial): released 4, not-affected 3, needed 1. https://ubuntu.com/security/CVE-2026-27857

Affected software / configurations for CVE-2026-27857

Vendor Product Version Raw CPE
dovecot dovecot < 2.4.3 cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:*
open-xchange dovecot < 2.3.22.1 cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*
open-xchange dovecot >= 3.0.0, < 3.0.5 cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*
open-xchange dovecot >= 3.1.0, < 3.1.4 cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*

References for CVE-2026-27857

cvelogic Threat Intelligence