CVE-2026-67445· NVD / CVE Program· CNA GitHub_M

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

Noroxi assessment

Priority: Monitor (action score 21/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.50% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: axllent mailpit 1.30.4.

Low priority for now. Upgrade to axllent mailpit 1.30.4 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

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.

MediumCVSS 5.3 · v3.1—No exploit Fix available

Published: Aug 20, 2026
Updated: Sep 18, 2026
EPSS: 0.5% · 41th percentile
CWE: CWE-400

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 21 / 40 · 5.3 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.5%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · GitHub_M: 5.3; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

axllent mailpit
- < 1.30.4affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Go	github.com/axllent/mailpit	before 1.30.4	1.30.4

Same product

axllent: all records

Other highest-scoring records for the same primary product.

CVE-2026-27808Mailpit is Vulnerable to Server-Side Request Forgery (SSRF) via Link Check API
34Monitor
CVE-2026-45711Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-controlled message IDs
32Monitor
CVE-2026-45713Mailpit: Unauthenticated remote memory-exhaustion DoS via unlimited SMTP DATA and /api/v1/send body sizes
30Monitor
CVE-2026-23845Mailpit Vulnerable to Server-Side Request Forgery (SSRF) via HTML Check API
30Monitor
CVE-2026-84697Mailpit SSRF Deny List Bypass via Azure Metadata and IPv6 Prefix
27Monitor
CVE-2026-67448Mailpit: WebSocket origin check bypass via percent-encoded path (regression of CVE-2026-22689)
26Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
axllent mailpit	1.30.4 · description	Vendor (CNA)
Go:github.com/axllent/mailpit	1.30.4	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

axllent/mailpitcommit 993bed9

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-4571331 days apartMailpit: Unauthenticated remote memory-exhaustion DoS via unlimited SMTP DATA and /api/v1/send body sizes
30Monitor
CVE-2026-674460 days apartMailpit: Thumbnail generation decodes unbounded image dimensions before scaling
21Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: low · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: Low

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

nvd-secondary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {2  return node.children.map(expand);3}

Fixed

1const MAX_DEPTH = 32;2function expand(node, depth = 0) {3  if (depth > MAX_DEPTH) throw new Error("too deep");4  return node.children.map((c) => expand(c, depth + 1));5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

Fix✗ → ✓Sep 28, 2026, 10:47 PM UTC

For records you follow, these changes also arrive as notifications. →

References

github.com/axllent/mailpit/commit/993bed95b3c74d95231af93bd0e0d4c3d5b4db4d

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records