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CVE-2026-45712— Mailpit: Concurrent map read & write in proxy CSS rewriter - remote unauth crash (fatal error: concurrent map read and map write)

Quick assessment

Affected
axllent mailpit
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

axllent mailpit是axllent个人开发者开源的一款邮件测试与调试工具。 Ralph Slooten Mailpit 1.30.0之前版本存在安全漏洞，该漏洞源于在未持有assetsMutex的情况下读取包级assets map缓存，与并发写入操作产生竞争条件，可能导致Go运行时发生致命错误，导致Mailpit进程退出，影响SMTP、POP3和HTTP服务。

CVSS 5.9 · Medium EPSS 0.34% · P25

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
axllent mailpit < 1.30.0 affected
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I. Basic Information for CVE-2026-45712

Vulnerability Information
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Vulnerability Title
Mailpit: Concurrent map read & write in proxy CSS rewriter - remote unauth crash (fatal error: concurrent map read and map write)
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
使用共享资源的并发执行不恰当同步问题(竞争条件)
Source: CVE Program / CVE List V5
Vulnerability Title
Ralph Slooten Mailpit 竞争条件问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
axllent mailpit是axllent个人开发者开源的一款邮件测试与调试工具。 Ralph Slooten Mailpit 1.30.0之前版本存在安全漏洞，该漏洞源于在未持有assetsMutex的情况下读取包级assets map缓存，与并发写入操作产生竞争条件，可能导致Go运行时发生致命错误，导致Mailpit进程退出，影响SMTP、POP3和HTTP服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
axllent mailpit < 1.30.0 -

II. Public POCs for CVE-2026-45712

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III. Intelligence Information for CVE-2026-45712

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Vendor Advisories for CVE-2026-45712 (1)

Vendor Pages for CVE-2026-45712 (1)

Same Patch Batch · axllent · 2026-07-20 · 5 CVEs total

CVE-2026-45713 7.5 HIGH Mailpit: Unauthenticated remote memory-exhaustion DoS via unlimited SMTP DATA and /api/v1/
CVE-2026-45711 5.9 MEDIUM Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-control
CVE-2026-45709 5.8 MEDIUM Mailpit has an incomplete fix for GHSA-6jxm: HTML check still permits SSRF to private/loop
CVE-2026-48824 5.3 MEDIUM Mailpit: Sibling-endpoint memory-exhaustion DoS via unbounded JSON body on /api/v1/message

IV. Related Vulnerabilities

Same product: mailpit
Same vendor: axllent
Same weakness: CWE-362

V. Comments for CVE-2026-45712

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