CVE-2026-55187Public exploitNetwork attack vector

Internal service discovery via IPv6 SSRF bypass

Published Jul 10, 2026 · Updated Jul 10, 2026

Server-side request forgery in Mailpit before 1.30.2 allows remote attackers to map internal service reachability through the Link Check API. The safeDialContext path trusts tools.IsInternalIP, whose standard-library predicates fail to reject NAT64, 6to4, ISATAP, IPv4-compatible, and reserved IPv6 forms. The default deployment permits unauthenticated email delivery and API access; returned status and error data reveal reachability but not response bodies.

CVSS severity5.8
Medium
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Server-side request forgery in Mailpit before 1.30.2 allows remote attackers to map internal service reachability through the Link Check API. The safeDialContext path trusts tools.IsInternalIP, whose standard-library predicates fail to reject NAT64, 6to4, ISATAP, IPv4-compatible, and reserved IPv6 forms. The default deployment permits unauthenticated email delivery and API access; returned status and error data reveal reachability but not response bodies.

The record

CVE
CVE-2026-55187
Published
Jul 10, 2026
Updated
Jul 10, 2026
Vendor
Axllent
Product
Mailpit
Classifications
CWE-918, CAPEC-664, T1046
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 10, 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=< 1.30.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Axllent · Mailpitversion=< 1.30.2

Published CVSS scores

5.8GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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.

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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 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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