CVE-2026-75006Network attack vector

SSRF via CSS hostname parsing bypass

Published Aug 17, 2026 · Updated Aug 17, 2026

SSRF in HTML e-mail handling in Roundcube Webmail before 1.6.18 and 1.7.3 allows remote attackers to reach local hosts via crafted CSS. The CSS proxy relies on rcube_utils::is_local_url() to reject local destinations, but that check mishandles nip.io and sslip.io hostnames and omits some local address ranges, so attacker-supplied stylesheet URLs can still resolve to internal, link-local, or carrier-grade NAT addresses. Exploitation requires delivery of an HTML message that causes Roundcube to fetch the referenced stylesheet; the reported consequences are SSRF against internal services and indirect disclosure of fetched network-reachable content or metadata.

CVSS severity5.8
Medium
EPSS probability0.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSRF in HTML e-mail handling in Roundcube Webmail before 1.6.18 and 1.7.3 allows remote attackers to reach local hosts via crafted CSS. The CSS proxy relies on rcube_utils::is_local_url() to reject local destinations, but that check mishandles nip.io and sslip.io hostnames and omits some local address ranges, so attacker-supplied stylesheet URLs can still resolve to internal, link-local, or carrier-grade NAT addresses. Exploitation requires delivery of an HTML message that causes Roundcube to fetch the referenced stylesheet; the reported consequences are SSRF against internal services and indirect disclosure of fetched network-reachable content or metadata.

The record

CVE
CVE-2026-75006
Published
Aug 17, 2026
Updated
Aug 17, 2026
Vendor
Roundcube
Product
Roundcube Webmail
Classifications
CWE-918
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 17, 2026Record 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=1.6.0 <1.6.18
  2. Affected versionversion=1.7.0 <1.7.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Roundcube · Roundcube Webmailversion=1.6.0 <1.6.18; version=1.7.0 <1.7.3

Published CVSS scores

5.8MITRECVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/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 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-918Server-Side Request Forgery (SSRF)

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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