Connect your agent
AdvisoriesCriticalCheck your lockfilePluginHow it worksPricing Connect your agent

Advisory record · GHSA-v3q9-hj7j-63hq

aiosmtplib vulnerable to SMTP command injection via CR/LF in sender/recipient address

CVSS 6.9 MediumEPSS 0.0053 · 45th percentile

Published by the GitHub Advisory Database at 7 Jul 2026, 23:40 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
aiosmtplibPyPI<5.1.15.1.1
Identifiers
GHSA-v3q9-hj7j-63hq · CVE-2026-53533 · PYSEC-2026-2338
Weakness (CWE)
CWE-77 · CWE-93
Tags
Published
7 Jul 2026
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

aiosmtplib versions before 5.1.1 do not reject carriage return or line feed characters in sender and recipient addresses passed to SMTP.mail(), rcpt(), vrfy(), expn(), and sendmail(). An application that passes attacker-influenced addresses into these calls lets an attacker inject additional SMTP commands into the session, which can cause the client to hang and possibly deny service. Upgrade to aiosmtplib 5.1.1 or later.

Written 4 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
6.9 Medium 4.0 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:H/SA:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0053, the 45th percentile, on 13 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:29 UTC First seen by agentprime
  2. 31 Oct 2026, 14:29 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.