# CVE-2026-45712: axllent Mailpit denial of service via race condition in proxy handler

Source: https://junglewise.ai/threats/cve-2026-45712-axllent-mailpit-denial-of-service-via-race-condition-in-proxy  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-20. Updated: 2026-07-20  
License: CC BY 4.0 with a link back

CVE-2026-45712 · Severity: medium · CVSS 5.9 · Published 2026-07-20

Mailpit is an email testing tool used by developers to capture and view outgoing emails during software development. A flaw in how the tool handles internal data allows a remote attacker to crash the entire application by sending specifically crafted requests. This results in a total service outage, preventing developers from receiving or testing emails until the process is manually restarted.

Technologies: [Axllent Mailpit](https://junglewise.ai/threats/technologies/mailpit), [github.com/axllent/mailpit (Go)](https://junglewise.ai/threats/technologies/github-com-axllent-mailpit). Vendors: [Axllent](https://junglewise.ai/threats/vendors/axllent), [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-45712 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-45712 being exploited in the wild.

**How severe is CVE-2026-45712?** Medium severity, with a CVSS score of 5.9, published 20 July 2026.

**Which products and versions are affected?** Axllent Mailpit < 1.30.0; github.com/axllent/mailpit (Go) < 1.30.0, SEMVER:introduced=0,fixed=1.30.0.

**Is there a fix for CVE-2026-45712?** Yes. github.com/axllent/mailpit (Go): upgrade to 1.30.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-45712 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-45712?** Check whether you run Axllent Mailpit or github.com/axllent/mailpit (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/axllent/mailpit (Go): upgrade to 1.30.0 or later

  ```sh
  go get github.com/axllent/mailpit@v1.30.0
  ```


## Technical details

A race condition exists in the Mailpit screenshot/print proxy (/proxy?data=...) due to improper synchronization of a package-level assets map. The application performs unsynchronized reads on the map while a background cleanup goroutine and CSS-rewriting logic perform synchronized writes. Because Go's runtime raises a non-recoverable fatal error upon detecting concurrent map access, the entire Mailpit process terminates, including SMTP, POP3, and HTTP listeners. An unauthenticated attacker can trigger this by planting a message with a stylesheet link and issuing concurrent requests to the proxy endpoint. The issue is fixed in version 1.30.0.

## Affected products

- axllent Mailpit < 1.30.0

## Identifiers

- CVE-2026-45712
- GHSA-w4vj-r5pg-3722
- GO-2026-5689

## Timeline

- 2026-05-14: patched: Version 1.30.0 released
- 2026-07-20: disclosed: CVE-2026-45712 published

## References

- [https://github.com/axllent/mailpit/releases/tag/v1.30.0](https://github.com/axllent/mailpit/releases/tag/v1.30.0)
- [https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722](https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722)

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