CVE-2023-23943Public exploitNetwork attack vector

Internal service scanning via unvalidated mail hosts

Published Feb 6, 2023 · Updated Mar 10, 2025

SSRF in Nextcloud Mail before 1.15.0 and 2.0.0 through 2.2.1 allows remote authenticated users to scan internal services. Account setup, autoconfiguration, connectivity-test, and Sieve endpoints opened server-side connections without rejecting local names or private IP addresses. A Mail user must submit a crafted SMTP, IMAP, or Sieve host, and blind connection results disclose whether services are reachable from the Nextcloud server.

CVSS severity5.0
Medium
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSRF in Nextcloud Mail before 1.15.0 and 2.0.0 through 2.2.1 allows remote authenticated users to scan internal services. Account setup, autoconfiguration, connectivity-test, and Sieve endpoints opened server-side connections without rejecting local names or private IP addresses. A Mail user must submit a crafted SMTP, IMAP, or Sieve host, and blind connection results disclose whether services are reachable from the Nextcloud server.

The record

CVE
CVE-2023-23943
Published
Feb 6, 2023
Updated
Mar 10, 2025
Vendor
Nextcloud GmbH
Product
Security Advisories
Classifications
CWE-918, CAPEC-664, T1046
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 6, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 10, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=< 1.15.0
  2. Affected versionversion=>= 2.0.0, < 2.2.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Security Advisoriesversion=< 1.15.0; version=>= 2.0.0, < 2.2.2

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
5.0GitHub CNACVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N
3.5GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
CAPEC-664Server Side Request Forgery
T1046Network Service Discovery

Public exploit references

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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