CVE-2026-27857: dovecot Uncontrolled Resource Consumption
Vulnerability summary
CVE-2026-27857 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in dovecot. EPSS estimates a 0.80% chance of exploitation in the next 30 days, higher than 56% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 18 · Related 5Timeline
- 27-03-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
Description
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.
CVSS metrics
5 scores · 5 sources · 1 version- CVE.orgCNA4.3MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:LDiffers
- OSV · AlpineEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.80%
Chance of exploitation in the next 30 days
Percentile
56%
Versus all other CVEs
30-day change
+0.14 pp
From 0.67% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
- CWE-770Allocation of Resources Without Limits or ThrottlingThe product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.
Affected systems
Alpine1 product
- dovecot≥ 3.0.0, < 2.4.3-r0
Debian1 product
- dovecot< 1:2.3.19.1+dfsg1-2.1+deb12u2 | < 1:2.4.1+dfsg1-6+deb13u4 | < 1:2.4.3+dfsg1-1
Dovecot1 product
- dovecot< 2.4.3
Open-xchange1 product
- dovecot< 2.3.22.1 | ≥ 3.0.0, < 3.0.5 | ≥ 3.1.0, < 3.1.4
Open-xchange gmbh1 product
- ox dovecot pro≤ 2.3.0
Ubuntu1 product
- dovecotAll versions (No fix recorded) | < 1:2.3.16+dfsg1-3ubuntu2.7 | < 1:2.3.21+dfsg1-2ubuntu6.3 | < 1:2.4.1+dfsg1-5ubuntu4.1
6 vendors · 6 products
