CVE-2021-26090Network attack vector

Service interruption via Webmail login memory leak

Published Jul 12, 2021 · Updated Oct 25, 2024

Memory leak in Fortinet FortiMail Webmail 6.4.0 through 6.4.4 and 6.2.0 through 6.2.6 allows remote attackers to interrupt service. The Webmail login-request path fails to release allocated memory after processing specifically crafted unauthenticated requests, allowing repeated requests to consume available memory. No credentials or user interaction are required; the documented consequence is memory exhaustion and denial of service, not data disclosure or modification.

CVSS severity7.5
High
EPSS probability1.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory leak in Fortinet FortiMail Webmail 6.4.0 through 6.4.4 and 6.2.0 through 6.2.6 allows remote attackers to interrupt service. The Webmail login-request path fails to release allocated memory after processing specifically crafted unauthenticated requests, allowing repeated requests to consume available memory. No credentials or user interaction are required; the documented consequence is memory exhaustion and denial of service, not data disclosure or modification.

The record

CVE
CVE-2021-26090
Published
Jul 12, 2021
Updated
Oct 25, 2024
Vendor
Fortinet
Product
FortiMail
Classifications
CWE-401, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 25, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=FortiMail 6.4.0 through 6.4.4 and 6.2.0 through 6.2.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fortinet · FortiMailversion=FortiMail 6.4.0 through 6.4.4 and 6.2.0 through 6.2.6

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
5.3FortinetCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
T1499.002Service Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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