How severe is CVE-2026-15340?

CVE-2026-15340 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-15340 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-15340?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2026-15340 published?

CVE-2026-15340 was published on 2026-10-09 and last updated on 2026-10-11.

CVE-2026-15340

CVE-2026-15340 is a critical-severity vulnerability with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-120.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v4: 9.3
EPSS exploit prediction: 1% (48th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Published: 2026-10-09
Last modified: 2026-10-11

Description

lwIP SMTP client does not check the size of inputs, potentially allowing a buffer overflow.

Frequently asked questions

What is CVE-2026-15340?: lwIP SMTP client does not check the size of inputs, potentially allowing a buffer overflow.
How severe is CVE-2026-15340?: CVE-2026-15340 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-15340 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-15340?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-15340 published?: CVE-2026-15340 was published on 2026-10-09 and last updated on 2026-10-11.

References

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