CVE-2023-51766

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under NVD CVSS v3. EPSS exploit probability: 1.1%, top 39% of all CVEs by exploit prediction. GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: epss, ghsa, nvd
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 5.3Exploit: None knownExposed: 0

A fix is available — apply it.

Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING configurations. Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass of an SPF protection mechanism. This occurs because Exim supports . but some other popular e-mail servers do not.

CVSS v3
5.3
EG Score
5.3(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: 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
Severity53% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
64%
KEV
Not listed

Published

December 24, 2023

Last Modified

June 17, 2026

References (42)

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntueximon4 (4.96-17ubuntu2.2) @ mantic2026-05-24ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(5 across 5 ecosystems)
Debian:10(1)
PackageVulnerable rangeFixed inDependents
exim44.92-8 ... 4.92-8+deb10u8 (12 versions)4.92-8+deb10u9—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
exim44.94.2-7, 4.94.2-7+deb11u14.94.2-7+deb11u2—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
exim44.96-15, 4.96-15+deb12u1, 4.96-15+deb12u2, 4.96-15+deb12u34.96-15+deb12u4—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
exim4—4.97-3—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
exim4—4.97-3—

Weakness Classification(1)

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

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 6× in last 7d / 31× 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.

Showing the most recent 100 of 166 total refreshes for this CVE.

  1. 2026-09-18 19:26 UTCEPSS rescore
  2. 2026-09-17 19:25 UTCEPSS rescore
  3. 2026-09-16 14:06 UTCEPSS rescore
  4. 2026-09-16 05:11 UTCEPSS rescore
  5. 2026-09-15 03:08 UTCEPSS rescore
  6. 2026-09-13 16:44 UTCEPSS rescore
  7. 2026-09-12 14:58 UTCEPSS rescore
  8. 2026-09-11 14:50 UTCEPSS rescore
  9. 2026-09-11 09:34 UTCEPSS rescore
  10. 2026-09-08 21:58 UTCEPSS rescore
  11. 2026-09-07 15:59 UTCEPSS rescore
  12. 2026-09-06 13:46 UTCEPSS rescore
  13. 2026-09-06 13:45 UTCEPSS rescore
  14. 2026-09-05 15:26 UTCEPSS rescore
  15. 2026-09-04 13:58 UTCEPSS rescore
  16. 2026-09-04 05:04 UTCEPSS rescore
  17. 2026-09-03 09:30 UTCOSV refresh
  18. 2026-09-02 14:10 UTCEPSS rescore
  19. 2026-09-02 14:09 UTCEPSS rescore
  20. 2026-09-01 13:51 UTCEPSS rescore
  21. 2026-09-01 04:35 UTCEPSS rescore
  22. 2026-08-30 19:15 UTCEPSS rescore
  23. 2026-08-30 01:20 UTCEPSS rescore
  24. 2026-08-28 21:39 UTCEPSS rescore
  25. 2026-08-27 14:23 UTCEPSS rescore
Show 75 more
  1. 2026-08-26 14:44 UTCEPSS rescore
  2. 2026-08-25 13:46 UTCEPSS rescore
  3. 2026-08-24 14:14 UTCEPSS rescore
  4. 2026-08-23 00:17 UTCEPSS rescore
  5. 2026-08-21 23:47 UTCEPSS rescore
  6. 2026-08-20 22:53 UTCEPSS rescore
  7. 2026-08-19 17:02 UTCEPSS rescore
  8. 2026-08-19 17:02 UTCEPSS rescore
  9. 2026-08-18 13:46 UTCEPSS rescore
  10. 2026-08-17 13:45 UTCEPSS rescore
  11. 2026-08-16 22:56 UTCOSV refresh
  12. 2026-08-16 14:54 UTCEPSS rescore
  13. 2026-08-16 02:12 UTCEPSS rescore
  14. 2026-08-15 01:28 UTCEPSS rescore
  15. 2026-08-13 21:58 UTCEPSS rescore
  16. 2026-08-12 13:49 UTCEPSS rescore
  17. 2026-08-11 13:40 UTCEPSS rescore
  18. 2026-08-10 23:57 UTCEPSS rescore
  19. 2026-08-09 13:44 UTCEPSS rescore
  20. 2026-08-09 13:44 UTCEPSS rescore
  21. 2026-08-08 16:35 UTCEPSS rescore
  22. 2026-08-07 16:25 UTCEPSS rescore
  23. 2026-08-06 13:45 UTCEPSS rescore
  24. 2026-08-05 19:15 UTCEPSS rescore
  25. 2026-08-04 15:07 UTCEPSS rescore
  26. 2026-08-04 10:35 UTCEPSS rescore
  27. 2026-08-03 10:34 UTCEPSS rescore
  28. 2026-08-03 10:34 UTCEPSS rescore
  29. 2026-08-02 02:25 UTCEPSS rescore
  30. 2026-08-02 02:25 UTCEPSS rescore
  31. 2026-08-01 17:06 UTCOSV refresh
  32. 2026-08-01 04:14 UTCEPSS rescore
  33. 2026-07-30 16:26 UTCEPSS rescore
  34. 2026-07-30 16:26 UTCEPSS rescore
  35. 2026-07-30 01:28 UTCEPSS rescore
  36. 2026-07-28 15:34 UTCEPSS rescore
  37. 2026-07-28 15:34 UTCEPSS rescore
  38. 2026-07-27 14:10 UTCEPSS rescore
  39. 2026-07-26 14:52 UTCEPSS rescore
  40. 2026-07-25 14:16 UTCEPSS rescore
  41. 2026-07-24 14:16 UTCEPSS rescore
  42. 2026-07-24 14:16 UTCEPSS rescore
  43. 2026-07-23 14:16 UTCEPSS rescore
  44. 2026-07-23 02:29 UTCEG score recompute
  45. 2026-07-22 23:15 UTCEG score recompute▲ 1.00
  46. 2026-07-22 14:06 UTCEPSS rescore
  47. 2026-07-21 15:23 UTCEPSS rescore
  48. 2026-07-21 15:23 UTCEPSS rescore
  49. 2026-07-20 17:06 UTCEPSS rescore
  50. 2026-07-19 14:29 UTCEPSS rescore
  51. 2026-07-19 14:29 UTCEPSS rescore
  52. 2026-07-19 02:27 UTCEPSS rescore
  53. 2026-07-18 10:03 UTCEPSS rescore
  54. 2026-07-18 10:03 UTCEPSS rescore
  55. 2026-07-16 17:01 UTCEPSS rescore
  56. 2026-07-15 16:56 UTCEPSS rescore
  57. 2026-07-15 16:56 UTCEPSS rescore
  58. 2026-07-15 01:59 UTCEPSS rescore
  59. 2026-07-15 01:59 UTCEPSS rescore
  60. 2026-07-15 00:10 UTCOSV refresh
  61. 2026-07-13 22:28 UTCEPSS rescore
  62. 2026-07-13 22:28 UTCEPSS rescore
  63. 2026-07-13 06:11 UTCEPSS rescore
  64. 2026-07-13 06:11 UTCEPSS rescore
  65. 2026-07-12 05:45 UTCEPSS rescore
  66. 2026-07-11 08:26 UTCEPSS rescore
  67. 2026-07-09 19:08 UTCEPSS rescore
  68. 2026-07-08 15:13 UTCEPSS rescore
  69. 2026-07-07 13:44 UTCEPSS rescore
  70. 2026-07-07 13:44 UTCEPSS rescore
  71. 2026-07-06 16:26 UTCEPSS rescore
  72. 2026-07-06 16:26 UTCEPSS rescore
  73. 2026-07-06 02:22 UTCEPSS rescore
  74. 2026-07-05 02:29 UTCEPSS rescore
  75. 2026-07-04 06:29 UTCEPSS rescore

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2023-51766?
CVE-2023-51766 is a medium vulnerability published on December 24, 2023. Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING configurations. Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass of an SPF protection mechanism. This occurs because Exim supports…
When was CVE-2023-51766 disclosed?
CVE-2023-51766 was first published in the National Vulnerability Database on December 24, 2023, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2023-51766 actively exploited?
CVE-2023-51766 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 35.8% of all scored CVEs.
What is the CVSS score of CVE-2023-51766?
CVE-2023-51766 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2023-51766?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-51766, 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.

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