CVE-2026-45712: CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') in axllent mailpit
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.
AI Analysis
Technical Summary
CVE-2026-45712 describes a race condition vulnerability in the Mailpit email testing tool before version 1.30.0. The vulnerability arises because the /proxy?data=… endpoint accesses a package-level map cache without proper synchronization during reads, while a cleanup goroutine and CSS-rewriting code write to the map under a mutex. This concurrent unsynchronized read and synchronized write triggers a fatal runtime error in Go, causing the entire Mailpit process to exit unexpectedly and disrupting all associated network services. The issue is fixed in Mailpit version 1.30.0.
Potential Impact
Exploitation of this race condition causes the Mailpit process to crash, resulting in denial of service by shutting down SMTP, POP3, and HTTP listeners. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
A patch is available in Mailpit version 1.30.0 that fixes the race condition by properly synchronizing access to the shared map. Users should upgrade to version 1.30.0 or later to remediate this vulnerability. No other mitigation guidance is provided.
CVE-2026-45712: CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') in axllent mailpit
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.
CVSS v3.1
Score 5.9medium
Affected software
pkg:golang/github.com/axllent/mailpitRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-45712 describes a race condition vulnerability in the Mailpit email testing tool before version 1.30.0. The vulnerability arises because the /proxy?data=… endpoint accesses a package-level map cache without proper synchronization during reads, while a cleanup goroutine and CSS-rewriting code write to the map under a mutex. This concurrent unsynchronized read and synchronized write triggers a fatal runtime error in Go, causing the entire Mailpit process to exit unexpectedly and disrupting all associated network services. The issue is fixed in Mailpit version 1.30.0.
Potential Impact
Exploitation of this race condition causes the Mailpit process to crash, resulting in denial of service by shutting down SMTP, POP3, and HTTP listeners. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
A patch is available in Mailpit version 1.30.0 that fixes the race condition by properly synchronizing access to the shared map. Users should upgrade to version 1.30.0 or later to remediate this vulnerability. No other mitigation guidance is provided.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-05-13T05:51:48.665Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a5e3e5d2a4a8d5989464d9f
Added to database: 07/20/2026, 15:27:25 UTC
Last enriched: 07/20/2026, 15:42:35 UTC
Last updated: 07/21/2026, 02:16:16 UTC
Views: 12
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