Critical severity · published Oct 9, 2026
CVE-2026-15340
Savannah lwIP SMTP client Classic Buffer Overflow
9.8
CVSS
0.4%
EPSS
No
On KEV
Description
lwIP SMTP client does not check the size of inputs, potentially allowing a buffer overflow.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 30% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
LS
lwIP SMTP client · Savannah
2.2.1 · source: vendor
In the news
ThreatIntelCritical
Savannah lwIP SMTP client
View CSAF
Summary
Successful exploitation of this vulnerability could crash the device being accessed; a buffer overflow condition may allow remote code execution.
The following versions of Savannah lwIP SMTP client are affected:
lwIP SMTP client 2.2.1 (CVE-2026-15340)
CVSS
Vendor
Equipment
v3 9.8
Savannah
lwIP SMTP client
1 Vulnerability
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Background
Critical Infrastructure Sectors: Energy, Water and Wastewater Systems
Countries/Areas Deployed: Worldwide
Company Headquarters Location: Sweden
Vulnerabilities
CVE-2026-15340
lwIP SMTP client does not check the size of inputs, potentially allowing a buffer overflow.
Read More
1 Affected Product
Savannah lwIP SMTP client: 2.2.1
Product Status: known_affected
Remediations
Mitigation xchglabs reports that the vulnerability was fixed and released in the following patch: patch_125_smtp_txbuf.diff . This is available as available as git commit (614420f82c8729d070e01464c0dddb3c9525c772)
Additional Metrics
Relevant CWE: CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
CVSS Version
Base Score
Base Severity
Vector String
3.1
9.8
CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
4.0
9.3
CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N...
Oct 6, 2026·CISA Advisories
