CVE-2026-53533

MEDIUMPre-NVD 6.96.9
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (42nd percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
6.9EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 6.9Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
6.9MEDIUMmedium confidence
EG Risk
31
EG Risk 31/100

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 (value × EchelonGraph’s weight)
Severity69% × 45%
The EG Score, 6.9 of 10.
Exploitation0.5% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
42nd
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

July 7, 2026

Last Modified

September 18, 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 advisoryMentions a patch (unverified)

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

(4 across 4 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
aiosmtplib2.0.0-1 ... 5.1.3-1 (14 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
aiosmtplib4.0.0-1 ... 5.1.3-1 (10 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
aiosmtplib4.0.0-1 ... 5.1.0-3 (8 versions)
  • every version up to 5.1.2-1: fixed in 5.1.2-1
—
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
aiosmtplib0.1 ... 5.1.0 (36 versions)
  • every version up to 5.1.1: fixed in 5.1.1
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 33× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  2. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  3. 2026-10-12 15:57 UTCEG score recompute
  4. 2026-10-11 19:40 UTCEG score recompute
  5. 2026-10-11 16:55 UTCEG score recompute
  6. 2026-10-11 14:19 UTCEG score recompute
  7. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  8. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  9. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  10. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  11. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  12. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  13. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  14. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  15. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  16. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  17. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  18. 2026-10-01 16:25 UTCEG score recompute
  19. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  20. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  21. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  22. 2026-09-28 13:34 UTCEG score recompute
  23. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  24. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  25. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
Show 48 more
  1. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  2. 2026-09-23 06:15 UTCEG score recompute
  3. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  4. 2026-09-18 20:35 UTCEG score recompute
  5. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  6. 2026-09-18 05:48 UTCEG score recompute
  7. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  8. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  9. 2026-09-14 09:33 UTCEG score recompute
  10. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  11. 2026-09-13 08:29 UTCEG score recompute
  12. 2026-09-12 03:41 UTCEG score recompute
  13. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  14. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  15. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  16. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  17. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  18. 2026-09-05 22:52 UTCEG score recompute
  19. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  20. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  21. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  22. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  23. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  24. 2026-08-30 07:40 UTCEG score recompute
  25. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  26. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  27. 2026-08-27 21:54 UTCEG score recompute
  28. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  29. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  30. 2026-08-26 12:57 UTCEG score recompute
  31. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  32. 2026-08-25 00:44 UTCEG score recompute
  33. 2026-08-23 23:39 UTCEG score recompute
  34. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  35. 2026-08-22 22:35 UTCEG score recompute
  36. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  37. 2026-08-21 21:30 UTCEG score recompute
  38. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  39. 2026-08-19 19:21 UTCEG score recompute
  40. 2026-08-19 18:38 UTCEG score recompute
  41. 2026-08-19 17:04 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  42. 2026-08-18 18:25 UTCEG score recompute
  43. 2026-08-18 18:07 UTCEG score recomputeFirst assessed: 6.9 MEDIUM
  44. 2026-08-18 18:04 UTCMITRE cvelistV5CVSS v3 → 6.9 · CVSS v4 → 6.9
  45. 2026-08-01 02:20 UTCEG score recompute
  46. 2026-07-26 12:34 UTCEG score recompute
  47. 2026-07-23 03:19 UTCEG score recompute
  48. 2026-07-08 00:13 UTCEG score recompute

Related CVEs(same product + same CWE)

Same product

2 shown

PyPI:aiosmtplib · Debian:12:aiosmtplib

Frequently asked(5)

What is CVE-2026-53533?
CVE-2026-53533 is a medium-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-53533 published?
The CVE record for CVE-2026-53533 was published on July 7, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 18, 2026; the record at its source may have been updated since.
Is CVE-2026-53533 actively exploited?
CVE-2026-53533 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (42nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-53533?
CVE-2026-53533 has a CVSS base score of 6.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-53533?
A fix for CVE-2026-53533 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-53533 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-53533

Explore →

Is Your Infrastructure Affected by CVE-2026-53533?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Book a Demo →Browse All CVEs