CVE-2026-53533

MEDIUMPre-NVD 6.96.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 69% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
6.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.9Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

aiosmtplib is an asynchronous SMTP client for use with asyncio. Prior to 5.1.1, SMTP.mail(), SMTP.rcpt(), SMTP.vrfy(), and SMTP.expn() send caller-supplied addresses without rejecting embedded CR or LF bytes. Data after the line break is framed as additional standalone SMTP command lines, allowing an attacker who influences an envelope sender or recipient to inject commands such as MAIL FROM, RCPT TO, RSET, DATA, or AUTH. SMTP.sendmail() and SMTP.send() without a Message object pass addresses through the affected methods, while SMTP.send_message() is not affected. Successful injection can desynchronize the command-response pipeline, hang the SMTP instance, or send an arbitrary message without requiring attacker control of the SMTP server. This issue is fixed in version 5.1.1.

CVSS v3
6.9
EG Score
6.9(medium)
EG Risk
31(Track)
EG Risk 31/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity69% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
31%
KEV
Not listed

Published

July 7, 2026

Last Modified

August 19, 2026

Advisory Details (3)

Auto-updated Aug 18, 2026
Patch available. Sources: github_commit, github_release, github.
github_release Patch Available

5.1.1

Patch available: cole/aiosmtplib v5.1.1

https://github.com/cole/aiosmtplib/releases/tag/v5.1.1
github_commit Patch Available

commit 8eaf6efc9a8f (cole/aiosmtplib)

Patch available: cole/aiosmtplib v5.1.1 (contains commit 8eaf6efc9a8f)

https://github.com/cole/aiosmtplib/commit/8eaf6efc9a8f59e2e09d3ef11246a058c46bd3ba
github Patch Available

aiosmtplib: SMTP command injection via CR/LF in sender/recipient address · Advisory · cole/aiosmtplib · GitHub

https://github.com/cole/aiosmtplib/security/advisories/GHSA-v3q9-hj7j-63hq

Vendor Advisories for CVE-2026-53533(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
aiosmtplib0.1 ... 5.1.0 (36 versions)5.1.1—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 22× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-30 07:40 UTCEG score recompute
  2. 2026-08-30 01:22 UTCEPSS rescore
  3. 2026-08-28 21:41 UTCEPSS rescore
  4. 2026-08-27 21:54 UTCEG score recompute
  5. 2026-08-27 14:25 UTCEPSS rescore
  6. 2026-08-26 14:46 UTCEPSS rescore
  7. 2026-08-26 12:57 UTCEG score recompute
  8. 2026-08-25 13:49 UTCEPSS rescore
  9. 2026-08-25 00:44 UTCEG score recompute
  10. 2026-08-23 23:39 UTCEG score recompute
  11. 2026-08-23 00:19 UTCEPSS rescore
  12. 2026-08-22 22:35 UTCEG score recompute
  13. 2026-08-21 23:49 UTCEPSS rescore
  14. 2026-08-21 21:30 UTCEG score recompute
  15. 2026-08-20 22:55 UTCEPSS rescore
  16. 2026-08-19 19:21 UTCEG score recompute
  17. 2026-08-19 18:38 UTCEG score recompute
  18. 2026-08-19 17:04 UTCEPSS rescore
  19. 2026-08-18 18:25 UTCEG score recompute
  20. 2026-08-18 18:07 UTCEG score recompute▲ 6.90
  21. 2026-08-18 18:04 UTCMITRE cvelistV5CVSS v3 → 6.9 · CVSS v4 → 6.9
  22. 2026-08-01 02:20 UTCEG score recompute
  23. 2026-07-26 12:34 UTCEG score recompute
  24. 2026-07-23 03:19 UTCEG score recompute
  25. 2026-07-08 00:13 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-53533?
CVE-2026-53533 is a medium vulnerability published on July 7, 2026. aiosmtplib is an asynchronous SMTP client for use with asyncio. Prior to 5.1.1, SMTP.mail(), SMTP.rcpt(), SMTP.vrfy(), and SMTP.expn() send caller-supplied addresses without rejecting embedded CR or LF bytes. Data after the line break is framed as additional standalone SMTP command lines, allowing…
When was CVE-2026-53533 disclosed?
CVE-2026-53533 was first published in the National Vulnerability Database on July 7, 2026, with the most recent update on August 19, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-53533 actively exploited?
CVE-2026-53533 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 68.6% of all scored CVEs.
What is the CVSS score of CVE-2026-53533?
CVE-2026-53533 has a CVSS v3 base score of 6.9 (NVD).
How do I remediate CVE-2026-53533?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-53533, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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