Vulnerability in Cole Aiosmtplib
CVE-2026-90467
aiosmtplib before 5.1.3 fails to properly validate email addresses supplied by callers, allowing attackers to inject ESMTP parameters into MAIL FROM and RCPT TO command lines. Attackers can craft malicious addresses containing spaces and angle brackets to append parameters like AUTH, NOTIFY, or ORCPT to envelope commands, forging authenticated identities or forcing delivery notifications to third parties.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.0 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (33.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 33rd percentile — 33.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
Weakness classification (CWE)
References
- github.com/cole/aiosmtplib/commit/2e1b210714974ccc9efd0d09a8f846cb9aeaaec2 (patch)
- github.com/cole/aiosmtplib/releases/tag/v5.1.3 (release-notes)
- github.com/cole/aiosmtplib/blob/v5.1.2/src/aiosmtplib/email.py (technical-description)
- github.com/cole/aiosmtplib (product)
- www.vulncheck.com/advisories/aiosmtplib-before-5.1.3-esmtp-parameter-injection-… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-90467?
- CVE-2026-90467 is a medium-severity vulnerability in Cole Aiosmtplib, classified under Argument Injection. CVSS score: 4.0/10. Published 2026-09-12.
- How severe is CVE-2026-90467?
- Medium severity. CVSS v3 base score is 4.0 out of 10.