TI-2026-47725 Aliases CVE-2026-67447 GHSA-r553-m4fv-5v97

Mailpit: SMTP DATA line reader buffers over-limit input before size enforcement

MEDIUM 63CWE-770Published 2026-08-20 · Updated 2026-08-21

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · Low
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-770.

Summary

Mailpit is an email testing tool and API for developers. From 1.30.0 until 1.30.5, Mailpit's internal/smtpd/smtpd.go readData() function calls bufio.Reader.ReadBytes before applying the len(data)+len(line) size check to the completed SMTP DATA line against Server.MaxSize. An unauthenticated SMTP client can send a single line larger than the configured MaxMessageSize, causing the full line to be allocated before Mailpit returns the 552 5.3.4 rejection. This post-fix gap remains after normal multi-line DATA accumulation was bounded, and concurrent oversized lines can create substantial memory pressure beyond the configured message-size cap. This issue is fixed in version 1.30.5.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00507 43rd percentileScored 2026-11-07

Fix Fixed mailpit (axllent): 1.30.5github.com/axllent/mailpit (Go): 1.30.5

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
axllent	mailpit	1.30.0 to before 1.30.5	1.30.5	Patch available	CNA
—	github.com/axllent/mailpit (Go)	1.30.0 to before 1.30.5	1.30.5	Patch available	GHSA-r553-m4fv-5v97

mailpit Vendoraxllent Affected 1.30.0 to before 1.30.5 Fixed in 1.30.5 Patch available CNA
github.com/axllent/mailpit (Go) Vendor— Affected 1.30.0 to before 1.30.5 Fixed in 1.30.5 Patch available GHSA-r553-m4fv-5v97

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:axllent:mailpit::::::::	—	—	axllent

cpe:2.3:a:axllent:mailpit:*:*:*:*:*:*:*:* Versions — — ·axllent

Remediation

Fix · CNA mailpit (axllent) Fixed in 1.30.5
Fix · GHSA-r553-m4fv-5v97 github.com/axllent/mailpit (Go) Fixed in 1.30.5 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-67447
2026-10-03 Alias added: GHSA-r553-m4fv-5v97

References

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-67447

Other 4

TI-2026-22161 Mailpit is Vulnerable to Server-Side Request Forgery (SSRF) via Link Check API CVSS 3.1HIGH 8.6
TI-2026-33452 Mailpit: Unauthenticated remote memory-exhaustion DoS via unlimited SMTP DATA and /api/v1/send body sizes CVSS 3.1HIGH 7.5
TI-2026-33450 Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-controlled message IDs CVSS 3.1HIGH 8.2
TI-2026-39868 Mailpit: Incomplete SSRF protection in Link Check API via IPv6 transition mechanisms (follow-up to CVE-2026-27808) CVSS 3.1MEDIUM 5.8
TI-2026-17561 Mailpit Proxy Endpoint is Vulnerable to Server-Side Request Forgery (SSRF) CVSS 3.1MEDIUM 5.8
TI-2026-47724 Mailpit: Thumbnail generation decodes unbounded image dimensions before scaling CVSS 3.1MEDIUM 5.3

See all 15 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences