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CVE-2026-21859

Mailpit Proxy Endpoint is Vulnerable to Server-Side Request Forgery (SSRF)

5.8 MediumFix available

Mailpit is an email testing tool and API for developers. Versions 1.28.0 and below have a Server-Side Request Forgery (SSRF) vulnerability in the /proxy endpoint, allowing attackers to make requests to internal network resources. The /proxy endpoint validates http:// and https:// schemes, but it does not block internal IP addresses, enabling attackers to access internal services and APIs. This vulnerability is limited to HTTP GET requests with minimal headers. The issue is fixed in version 1.28.1.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
None
Availability
None

Exploit likelihood

0.81%Up 0.8 points since Jan 8, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.8

Mailpit Proxy Endpoint is Vulnerable to Server-Side Request Forgery (SSRF)

Mailpit is an email testing tool and API for developers. Versions 1.28.0 and below have a Server-Side Request Forgery (SSRF) vulnerability in the /proxy endpoint, allowing attackers to make requests to internal network resources. The /proxy endpoint validates http:// and https:// schemes, but it does not block internal IP addresses, enabling attackers to access internal services and APIs. This vulnerability is limited to HTTP GET requests with minimal headers. The issue is fixed in version 1.28.1.

Record
CVE-2026-21859
CVSS 3.1
5.8 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
Weakness
CWE-918
Updated
2026-11-02
EUVDEUVD-2026-1038 5.8

Mailpit is an email testing tool and API for developers. Versions 1.28.0 and below have a Server-Side Request Forgery (SSRF) vulnerability in the /proxy endpoint, allowing attackers to make requests to internal network resources. The /proxy endpoint validates http:// and https:// schemes, but it does not block internal IP addresses, enabling attackers to access internal services and APIs. This vulnerability is limited to HTTP GET requests with minimal headers. The issue is fixed in version 1.28.1.

Record
EUVD-2026-1038
CVSS 3.1
5.8 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-8v65-47jx-7mfr 5.8

Mailpit Proxy Endpoint has Server-Side Request Forgery (SSRF) vulnerability

Summary

A Server-Side Request Forgery (SSRF) vulnerability exists in Mailpit's /proxy endpoint that allows attackers to make requests to internal network resources.

Description

The /proxy endpoint allows requests to internal network resources. While it validates http:// and https:// schemes, it does not block internal IP addresses, allowing attackers to access internal services and APIs.

Proof of Concept

Basic SSRF Request

GET /proxy?url=http://127.0.0.1:8025/api/v1/info

This returns internal API data including database path and runtime statistics.

Impact Assessment

1. Internal Network Scanning

Attacker can probe and discover internal services on the network.

2. Information Disclosure

Access to internal API data, database paths, and runtime statistics.

3. Email Content Access

Ability to read all captured emails via internal API endpoints.

4. Cloud Metadata Access

If deployed in cloud environments (AWS/GCP/Azure), potential access to instance metadata services (e.g., http://169.254.169.254/).

Attack Scenarios

Scenario 1: Development Environment Exposure

If Mailpit is accidentally exposed to the internet, attackers can leverage SSRF to access internal development resources and services.

Scenario 2: Container Escape Information

In containerized deployments, SSRF can reveal container metadata and internal service configurations.

Scenario 3: Lateral Movement

In corporate networks, SSRF can be used to discover and interact with internal services, facilitating lateral movement.

Mitigating Factors

This vulnerability is limited to HTTP GET requests with minimal headers. Additionally, Mailpit's web UI & API should be protected by basic authentication when exposed to the internet, which prevents access to the proxy endpoint.

References

Record
GHSA-8v65-47jx-7mfr
CVSS 3.1
5.8 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
Weakness
CWE-918
Updated
2026-11-02
NVD 5.8

Mailpit is an email testing tool and API for developers. Versions 1.28.0 and below have a Server-Side Request Forgery (SSRF) vulnerability in the /proxy endpoint, allowing attackers to make requests to internal network resources. The /proxy endpoint validates http:// and https:// schemes, but it does not block internal IP addresses, enabling attackers to access internal services and APIs. This vulnerability is limited to HTTP GET requests with minimal headers. The issue is fixed in version 1.28.1.

Record
CVE-2026-21859
CVSS 3.1
5.8 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-918
Updated
2026-11-02
OSV 5.8

Mailpit Proxy Endpoint is Vulnerable to Server-Side Request Forgery (SSRF)

Mailpit is an email testing tool and API for developers. Versions 1.28.0 and below have a Server-Side Request Forgery (SSRF) vulnerability in the /proxy endpoint, allowing attackers to make requests to internal network resources. The /proxy endpoint validates http:// and https:// schemes, but it does not block internal IP addresses, enabling attackers to access internal services and APIs. This vulnerability is limited to HTTP GET requests with minimal headers. The issue is fixed in version 1.28.1.

Record
CVE-2026-21859
CVSS 3.1
5.8 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
Weakness
CWE-918
Updated
2026-11-02
OSVGHSA-8v65-47jx-7mfr 5.8

Mailpit Proxy Endpoint has Server-Side Request Forgery (SSRF) vulnerability

Summary

A Server-Side Request Forgery (SSRF) vulnerability exists in Mailpit's /proxy endpoint that allows attackers to make requests to internal network resources.

Description

The /proxy endpoint allows requests to internal network resources. While it validates http:// and https:// schemes, it does not block internal IP addresses, allowing attackers to access internal services and APIs.

Proof of Concept

Basic SSRF Request

GET /proxy?url=http://127.0.0.1:8025/api/v1/info

This returns internal API data including database path and runtime statistics.

Impact Assessment

1. Internal Network Scanning

Attacker can probe and discover internal services on the network.

2. Information Disclosure

Access to internal API data, database paths, and runtime statistics.

3. Email Content Access

Ability to read all captured emails via internal API endpoints.

4. Cloud Metadata Access

If deployed in cloud environments (AWS/GCP/Azure), potential access to instance metadata services (e.g., http://169.254.169.254/).

Attack Scenarios

Scenario 1: Development Environment Exposure

If Mailpit is accidentally exposed to the internet, attackers can leverage SSRF to access internal development resources and services.

Scenario 2: Container Escape Information

In containerized deployments, SSRF can reveal container metadata and internal service configurations.

Scenario 3: Lateral Movement

In corporate networks, SSRF can be used to discover and interact with internal services, facilitating lateral movement.

Mitigating Factors

This vulnerability is limited to HTTP GET requests with minimal headers. Additionally, Mailpit's web UI & API should be protected by basic authentication when exposed to the internet, which prevents access to the proxy endpoint.

References

Record
GHSA-8v65-47jx-7mfr
CVSS 3.1
5.8 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
Weakness
CWE-918
Updated
2026-11-02
OSVGO-2026-4284 No score

Mailpit Proxy Endpoint has Server-Side Request Forgery (SSRF) vulnerability in github.com/axllent/mailpit

Mailpit Proxy Endpoint has Server-Side Request Forgery (SSRF) vulnerability in github.com/axllent/mailpit

Record
GO-2026-4284
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02
OSVSUSE-SU-2026:0142-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260114T191543 2026-01-14T19:15:43Z (jsc#PED-11136).

    Go CVE Numbering Authority IDs added or updated with aliases:

    • GO-2025-4248 CVE-2025-62690 GHSA-q66g-q98c-q454
    • GO-2025-4251 CVE-2025-63389 GHSA-f6mr-38g8-39rg
    • GO-2026-4273 CVE-2025-14987 GHSA-hmhp-gh8m-c8xp

  • Update to version 0.0.20260113T164240 2026-01-13T16:42:40Z (jsc#PED-11136).

    Go CVE Numbering Authority IDs added or updated with aliases:

    • GO-2025-4269 CVE-2025-15107 GHSA-43h9-hc38-qph5
    • GO-2025-4272 CVE-2025-14986 GHSA-p2gr-hm8g-q772
    • GO-2026-4274 CVE-2025-69413 GHSA-pc73-rj2c-wvf9
    • GO-2026-4275 CVE-2025-14273 GHSA-qvmc-92vg-6r35
    • GO-2026-4277 CVE-2026-21483 GHSA-jmr4-p576-v565
    • GO-2026-4278 CVE-2024-6717 GHSA-5mqx-rpxv-mvxj
    • GO-2026-4279 GHSA-4c5f-9mj4-m247
    • GO-2026-4280 GHSA-hjr9-wj7v-7hv8
    • GO-2026-4281 CVE-2025-62877 GHSA-6g8q-hp2j-gvwv
    • GO-2026-4283 CVE-2025-68954 GHSA-8c39-xppg-479c
    • GO-2026-4284 CVE-2026-21859 GHSA-8v65-47jx-7mfr
    • GO-2026-4285 GHSA-gg4x-fgg2-h9w9
    • GO-2026-4286 CVE-2026-0650 GHSA-rwp9-5g7q-73q3
    • GO-2026-4287 CVE-2026-21885 GHSA-xwh2-742g-w3wp
    • GO-2026-4289 CVE-2025-68151 GHSA-527x-5wrf-22m2
    • GO-2026-4290 CVE-2026-22253 GHSA-6jm8-x3g6-r33j
    • GO-2026-4292 CVE-2026-22688 GHSA-78h3-63c4-5fqc
    • GO-2026-4293 CVE-2026-22687 GHSA-pcwc-3fw3-8cqv
    • GO-2026-4295 CVE-2017-18895 GHSA-h742-xx59-r9pq
    • GO-2026-4296 CVE-2017-18893 GHSA-887v-xh2x-47cm
    • GO-2026-4297 CVE-2017-18894 GHSA-gg42-mwr6-p82c
    • GO-2026-4298 CVE-2017-18891 GHSA-vrh2-rprg-rgc6
    • GO-2026-4299 CVE-2017-18896 GHSA-63wg-qmrv-7q66
    • GO-2026-4300 CVE-2017-18898 GHSA-9589-mq83-f749
    • GO-2026-4301 CVE-2017-18897 GHSA-f7c3-7vp3-44p6
    • GO-2026-4302 CVE-2017-18904 GHSA-8pff-p3gx-w4jf
    • GO-2026-4303 CVE-2017-18900 GHSA-8q4v-35v6-g8wr
    • GO-2026-4304 CVE-2017-18901 GHSA-c253-8hr4-r8v9
    • GO-2026-4306 CVE-2017-18905 GHSA-g24c-fx4v-xg9w
    • GO-2026-4308 CVE-2025-60538 GHSA-mw8h-g64c-rxv4
    • GO-2026-4309 CVE-2026-22703 GHSA-whqx-f9j3-ch6m
Record
SUSE-SU-2026:0142-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/axllent/mailpit
Go
 through 1.28.0
1.28.1
github.com/axllent/mailpit
Go
 before 1.28.1
1.28.1
govulncheck-vulndb
openSUSE:Leap 15.6
From an advisory covering 31 CVEs
 before 0.0.20260114T191543-150000.1.137.1
0.0.20260114T191543-150000.1.137.1
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
SourceLinkDate
NucleiMailpit < 1.28.3 - Server-Side Request Forgery

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, Nuclei, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-21859 is a medium vulnerability (CVSS 5.8) in Axllent Mailpit, published January 6, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.81%, the 57th percentile. Fixed in github.com/axllent/mailpit 1.28.1.

References

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Left out here: 1,542 references and the rest of 1 source description. The JSON record has them.

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