CVE-2026-27858: dovecot Uncontrolled Resource Consumption
Vulnerability summary
CVE-2026-27858 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in dovecot. EPSS estimates a 1.04% chance of exploitation in the next 30 days, higher than 63.4% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 18 · Related 5Timeline
- 27-03-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
Description
Attacker can send a specifically crafted message before authentication that causes managesieve to allocate large amount of memory. Attacker can force managesieve-login to be unavailable by repeatedly crashing the process. Protect access to managesieve protocol, or install fixed version. No publicly available exploits are known.
CVSS metrics
4 scores · 4 sources · 1 version- 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
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
1.04%
Chance of exploitation in the next 30 days
Percentile
63%
Versus all other CVEs
30-day change
+0.25 pp
From 0.79% 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
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 | ≤ 3.1.0 | ≤ 2.4.0
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
5 vendors · 5 products
