TI-2026-47723 Aliases CVE-2026-67445 GHSA-w878-pj84-3j5v

Mailpit: SMTP command parser buffers unbounded command lines before syntax rejection

LOW 31CWE-400Published 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-400.

Summary

Mailpit is an email testing tool and API for developers. Prior to 1.30.4, Mailpit reads SMTP commands through internal/smtpd/smtpd.go session.readLine() using bufio.Reader.ReadString before session.parseLine() parses the verb or the RFC 5321 512-octet command-line limit is enforced. An unauthenticated remote SMTP client can send an oversized single command line that is fully allocated before syntax rejection or timeout, and the normal MaxMessageSize and DATA limits do not apply to this pre-DATA path. The same command reader is used by handleAuthLogin(), handleAuthPlain(), and handleAuthCramMD5() continuation lines, so concurrent oversized inputs can create memory pressure and reduce service availability. This issue is fixed in version 1.30.4.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00507 43rd percentileScored 2026-11-07

Fix Fixed mailpit (axllent): 1.30.4github.com/axllent/mailpit (Go): 1.30.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
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	before 1.30.4	1.30.4	Patch available	CNA
—	github.com/axllent/mailpit (Go)	before 1.30.4	1.30.4	Patch available	GHSA-w878-pj84-3j5v

mailpit Vendoraxllent Affected before 1.30.4 Fixed in 1.30.4 Patch available CNA
github.com/axllent/mailpit (Go) Vendor— Affected before 1.30.4 Fixed in 1.30.4 Patch available GHSA-w878-pj84-3j5v

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 1.30.4
Fix · GHSA-w878-pj84-3j5v github.com/axllent/mailpit (Go) Fixed in 1.30.4 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-67445
2026-10-03 Alias added: GHSA-w878-pj84-3j5v

References

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-67445

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-2026-47725 Mailpit: SMTP DATA line reader buffers over-limit input before size enforcement 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