# CVE-2026-45713: axllent Mailpit denial of service via unbounded message size

Source: https://junglewise.ai/threats/cve-2026-45713-axllent-mailpit-denial-of-service-via-unbounded-message-size  
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-2026-45713 · Severity: high · CVSS 7.5 · Published 2026-07-20

Mailpit is a tool used by developers to test email functionality during software development. A security flaw allows an unauthenticated attacker to send massive amounts of data to the tool, which can crash the service by consuming all available system memory. This results in a denial of service, preventing developers from testing their applications until the tool is 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-2026-45713 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-45713 being exploited in the wild.

**How severe is CVE-2026-45713?** High severity, with a CVSS score of 7.5, 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-2026-45713?** 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-2026-45713 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-45713?** 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

Mailpit prior to version 1.30.0 contains a resource exhaustion vulnerability (CWE-400/CWE-770). The SMTP server component includes a 'Server.MaxSize' field intended to limit DATA payloads, but this field was never initialized outside of test code, defaulting to 0 (no limit). Similarly, the HTTP '/api/v1/send' endpoint lacks a 'MaxBytesReader' implementation. An unauthenticated remote attacker can transmit arbitrarily large payloads, which undergo a 7-10x memory amplification during processing (parsing and indexing), leading to an Out-of-Memory (OOM) kill. Version 1.30.0 fixes this by introducing a default 50MB message size limit.

## Affected products

- axllent Mailpit < 1.30.0

## Identifiers

- CVE-2026-45713
- GHSA-fpxj-m5q8-fphw
- GO-2026-5376

## Timeline

- 2026-05-14: patched: Version 1.30.0 released with fix
- 2026-05-14: advisory: GitHub Security Advisory GHSA-fpxj-m5q8-fphw published
- 2026-07-20: disclosed: CVE-2026-45713 published to NVD

## 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-fpxj-m5q8-fphw](https://github.com/axllent/mailpit/security/advisories/GHSA-fpxj-m5q8-fphw)

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