Vulnerability · CVE-2026-27857
Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage.
Published Mar 27, 2026 · catalog updated Jul 15, 2026 · Sending "NOOP (((...)))" command
Check if you run it
No confirmed exploitation is on record for CVE-2026-27857. EPSS is 0.80%. Act only if a listed version of Sending "NOOP (((...)))" command is installed.
Gaps on this record
- The stored product name is a package slug. The name on this page is taken from the title (Sending "NOOP (((...)))" command).
- No version range is stored. A customer cannot check an installed version against this record.
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
- Severity
- High7.5
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 0.80%
- Remediation
- Advisory link
- Affected products
- cpe dovecot/dovecot · cpe open-xchange/dovecot
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.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- cpe dovecot/dovecotversion unspecified
- cpe open-xchange/dovecotversion unspecified
How to fix CVE-2026-27857
Recommended remediation
A patch or advisory reference is linked. Open the original publisher for availability by product version.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2026-27857. EPSS is 0.80%. Act only if a listed version of Sending "NOOP (((...)))" command is installed.
Which versions are affected?
Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
CWE-400: Uncontrolled Resource Consumption; CWE-770: Allocation of Resources Without Limits or Throttling. EPSS 0.80%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Mar 27, 2026 · NIST NVD
Detected
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
Jul 15, 2026 · NIST NVD
Updated
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
Sources
- CVE.orgVulnerability recordCVE-2026-27857
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-27857
30-day exploitation probability 0.8%
first.org - NIST NVDVulnerability recordCVE-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 possi
nvd.nist.gov
References
Freshness
Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.