CVE-2026-55187: CWE-918: Server-Side Request Forgery (SSRF) in axllent mailpit
Mailpit is an email testing tool and API for developers. Prior to 1.30.2, the remediation shipped for CVE-2026-27808 is incomplete because the tools.IsInternalIP deny-list in internal/tools/net.go relies on Go's standard library classification helpers and does not block IPv6 transition mechanisms or prefixes such as NAT64, 6to4, IPv4-compatible IPv6, ISATAP, fec0::/10, and 2001:db8::/32. An attacker who can deliver email and invoke POST /api/v1/message/{ID}/link-check can coerce the Link Check API's safeDialContext path into dialing internal destinations and can use status-code and error feedback to map internal service reachability, including cloud metadata endpoints. This issue is fixed in version 1.30.2.
AI Analysis
Technical Summary
CVE-2026-55187 is an SSRF vulnerability in the Mailpit email testing tool before version 1.30.2. The vulnerability arises because the deny-list for internal IP addresses in the tools.IsInternalIP function does not block certain IPv6 transition mechanisms and prefixes, such as NAT64, 6to4, IPv4-compatible IPv6, ISATAP, fec0::/10, and 2001:db8::/32. An attacker able to deliver email and invoke the POST /api/v1/message/{ID}/link-check endpoint can manipulate the Link Check API's safeDialContext to access internal destinations. This can be used to map internal services, including cloud metadata endpoints. The vulnerability has a CVSS 3.1 score of 5.8 (medium severity) and is fixed in Mailpit version 1.30.2.
Potential Impact
An attacker who can deliver email and invoke the vulnerable API endpoint can perform SSRF attacks to access internal network resources and map internal service reachability, including sensitive cloud metadata endpoints. This could lead to information disclosure about internal infrastructure. There is no indication of integrity or availability impact. No known exploits are reported in the wild.
Mitigation Recommendations
Upgrade Mailpit to version 1.30.2 or later, where this SSRF vulnerability is fixed by improving the internal IP address filtering logic. Since the vendor advisory states the issue is fixed in 1.30.2, applying this official fix is the recommended remediation. No other mitigations are indicated.
CVE-2026-55187: CWE-918: Server-Side Request Forgery (SSRF) in axllent mailpit
Description
Mailpit is an email testing tool and API for developers. Prior to 1.30.2, the remediation shipped for CVE-2026-27808 is incomplete because the tools.IsInternalIP deny-list in internal/tools/net.go relies on Go's standard library classification helpers and does not block IPv6 transition mechanisms or prefixes such as NAT64, 6to4, IPv4-compatible IPv6, ISATAP, fec0::/10, and 2001:db8::/32. An attacker who can deliver email and invoke POST /api/v1/message/{ID}/link-check can coerce the Link Check API's safeDialContext path into dialing internal destinations and can use status-code and error feedback to map internal service reachability, including cloud metadata endpoints. This issue is fixed in version 1.30.2.
CVSS v3.1
Score 5.8medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-55187 is an SSRF vulnerability in the Mailpit email testing tool before version 1.30.2. The vulnerability arises because the deny-list for internal IP addresses in the tools.IsInternalIP function does not block certain IPv6 transition mechanisms and prefixes, such as NAT64, 6to4, IPv4-compatible IPv6, ISATAP, fec0::/10, and 2001:db8::/32. An attacker able to deliver email and invoke the POST /api/v1/message/{ID}/link-check endpoint can manipulate the Link Check API's safeDialContext to access internal destinations. This can be used to map internal services, including cloud metadata endpoints. The vulnerability has a CVSS 3.1 score of 5.8 (medium severity) and is fixed in Mailpit version 1.30.2.
Potential Impact
An attacker who can deliver email and invoke the vulnerable API endpoint can perform SSRF attacks to access internal network resources and map internal service reachability, including sensitive cloud metadata endpoints. This could lead to information disclosure about internal infrastructure. There is no indication of integrity or availability impact. No known exploits are reported in the wild.
Mitigation Recommendations
Upgrade Mailpit to version 1.30.2 or later, where this SSRF vulnerability is fixed by improving the internal IP address filtering logic. Since the vendor advisory states the issue is fixed in 1.30.2, applying this official fix is the recommended remediation. No other mitigations are indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-16T15:20:43.086Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a516c2d68715ace43438234
Added to database: 07/10/2026, 22:03:25 UTC
Last enriched: 07/18/2026, 15:36:20 UTC
Last updated: 08/23/2026, 22:52:12 UTC
Views: 58
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