CVE-2020-28018

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 57% (99th percentile of EPSS-scored CVEs). 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, nvd
Elevated
9.8EG
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 57%
CISA-KEV: Not listedEPSS PROB: 57%CVSS: 9.8Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

Exim 4 before 4.94.2 allows Use After Free in smtp_reset in certain situations that may be common for builds with OpenSSL.

CVSS v3
9.8
EG Score
9.8CRITICALmedium confidence
EG Risk
71
EG Risk 71/100CISA SSVC

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
Severity98% × 45%
Exploitation57% × 40%
Automatability30% × 15%
CISA SSVC: Track at low, Track* at medium and Attend at high mission impact.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
57%
EPSS %ILE
99th
KEV
Not listed

CISA SSVCTrack at low, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (EG-KEV: elevated) · Automatable unknown (not published for this CVE) · Technical impact total (CVSS ≥ 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

May 6, 2021

Last Modified

November 21, 2024

Advisory Details (8)

Auto-updated Oct 4, 2026
🔬 Proof of concept available. Patch available.
generic

oss-security - Re: [CVE-2020-28018] Use-After-Free on Exim Question

http://www.openwall.com/lists/oss-security/2021/05/11/15
generic

oss-security - Re: [CVE-2020-28018] Use-After-Free on Exim Question

http://www.openwall.com/lists/oss-security/2021/05/11/14
generic🟡 PoC Available
https://www.exim.org/static/doc/security/CVE-2020-qualys/CVE-2020-28018-OCORK.txt
generic

oss-security - Re: [CVE-2020-28018] Use-After-Free on Exim Question

http://www.openwall.com/lists/oss-security/2021/05/12/3
generic

oss-security - Re: [CVE-2020-28018] Use-After-Free on Exim Question

http://www.openwall.com/lists/oss-security/2021/05/12/2
generic

oss-security - Re: [CVE-2020-28018] Use-After-Free on Exim Question

http://www.openwall.com/lists/oss-security/2021/05/11/6
generic🟡 PoC Available

oss-security - [CVE-2020-28018] Use-After-Free on Exim Question

http://www.openwall.com/lists/oss-security/2021/05/11/5
generic

oss-security - Re: [CVE-2020-28018] Use-After-Free on Exim Question

http://www.openwall.com/lists/oss-security/2021/05/11/17

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntueximon4 (4.94-15ubuntu1.2) @ hirsute2026-05-26ubuntu

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

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
exim4—
  • every version up to 4.94.2-1: fixed in 4.94.2-1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
exim4—
  • every version up to 4.94.2-1: fixed in 4.94.2-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
exim4—
  • every version up to 4.94.2-1: fixed in 4.94.2-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
exim4—
  • every version up to 4.94.2-1: fixed in 4.94.2-1
—

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 4× in last 7d / 20× 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 129 total refreshes for this CVE.

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

Publicly available exploits

(2 references)

Working exploit code is in the public domain (2 GitHub PoCs). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCzr0tt/CVE-2020-28018
    First seen May 18, 2021

    Exploit for Exim4 4.93 CVE-2020-28018

    Open source ↗
  • GitHub PoCdorkerdevil/CVE-2020-28018
    First seen May 15, 2021

    exim use after free exploit and detection

    Open source ↗

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2020-28018?
CVE-2020-28018 is a critical vulnerability published on May 6, 2021. Exim 4 before 4.94.2 allows Use After Free in smtp_reset in certain situations that may be common for builds with OpenSSL.
When was CVE-2020-28018 disclosed?
CVE-2020-28018 was first published on May 6, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2020-28018 actively exploited?
CVE-2020-28018 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 57% probability of exploitation in the next 30 days (99th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2020-28018?
CVE-2020-28018 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2020-28018?
A fix for CVE-2020-28018 is available: update to the fixed version the vendor names in its advisory.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2020-28018

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