CVE-2020-28018

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 56.8%, top 1% 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, nvd
Trending — 3 sources updated this weekElevated
9.8
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 57%
CISA-KEV: Not listedEPSS: 57%CVSS: 9.8Exploit: NoneExposed: 0

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
9.8(medium)
EG Risk
71(Track*)
EG Risk 71/100SSVC: 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
Severity98% × 45%
Exploitation57% × 40%
Automatability30% × 15%
Action: Watch closely — could escalate to Attend.
EPSS
99.0%
KEV
Not listed

Published

May 6, 2021

Last Modified

November 21, 2024

Advisory Details (8)

Auto-updated May 26, 2026
🔬 Proof of concept available. No patch confirmed yet.
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 / EcosystemFixed in / 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.

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 11× in last 7d / 33× 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. 2026-07-24 14:14 UTCEPSS rescore
  2. 2026-07-23 14:15 UTCEPSS rescore
  3. 2026-07-23 14:15 UTCEPSS rescore
  4. 2026-07-23 01:52 UTCEG score recompute
  5. 2026-07-22 22:38 UTCEG score recompute
  6. 2026-07-22 14:05 UTCEPSS rescore
  7. 2026-07-20 17:04 UTCEPSS rescore
  8. 2026-07-20 17:04 UTCEPSS rescore
  9. 2026-07-19 02:26 UTCEPSS rescore
  10. 2026-07-19 02:26 UTCEPSS rescore
  11. 2026-07-18 20:59 UTCOSV refresh
  12. 2026-07-16 16:59 UTCEPSS rescore
  13. 2026-07-15 16:55 UTCEPSS rescore
  14. 2026-07-15 16:55 UTCEPSS rescore
  15. 2026-07-15 01:57 UTCEPSS rescore
  16. 2026-07-13 22:27 UTCEPSS rescore
  17. 2026-07-13 22:27 UTCEPSS rescore
  18. 2026-07-13 06:10 UTCEPSS rescore
  19. 2026-07-13 06:10 UTCEPSS rescore
  20. 2026-07-12 05:44 UTCEPSS rescore
  21. 2026-07-11 08:25 UTCEPSS rescore
  22. 2026-07-11 08:25 UTCEPSS rescore
  23. 2026-07-09 19:07 UTCEPSS rescore
  24. 2026-07-04 06:29 UTCEPSS rescore
  25. 2026-07-04 06:29 UTCEPSS rescore
Show 55 more
  1. 2026-07-01 04:18 UTCOSV refresh
  2. 2026-06-30 23:20 UTCEPSS rescore
  3. 2026-06-30 23:20 UTCEPSS rescore
  4. 2026-06-28 04:54 UTCEPSS rescore
  5. 2026-06-28 04:54 UTCEPSS rescore
  6. 2026-06-27 03:06 UTCEPSS rescore
  7. 2026-06-27 03:06 UTCEPSS rescore
  8. 2026-06-25 13:48 UTCEPSS rescore
  9. 2026-06-24 14:03 UTCEPSS rescore
  10. 2026-06-24 14:03 UTCEPSS rescore
  11. 2026-06-23 21:31 UTCEPSS rescore
  12. 2026-06-23 21:31 UTCEPSS rescore
  13. 2026-06-21 14:54 UTCEPSS rescore
  14. 2026-06-21 14:54 UTCEPSS rescore
  15. 2026-06-21 01:57 UTCEPSS rescore
  16. 2026-06-17 17:50 UTCEPSS rescore
  17. 2026-06-16 17:50 UTCEPSS rescore
  18. 2026-06-15 17:46 UTCEPSS rescore
  19. 2026-06-13 22:58 UTCEPSS rescore
  20. 2026-06-13 07:13 UTCOSV refresh
  21. 2026-06-12 23:10 UTCEPSS rescore
  22. 2026-06-11 13:58 UTCEPSS rescore
  23. 2026-06-10 22:16 UTCEPSS rescore
  24. 2026-06-10 13:20 UTCEPSS rescore
  25. 2026-06-07 15:23 UTCEPSS rescore
  26. 2026-06-07 15:23 UTCEPSS rescore
  27. 2026-06-07 15:23 UTCEPSS rescore
  28. 2026-06-06 13:46 UTCEPSS rescore
  29. 2026-06-06 13:45 UTCEPSS rescore
  30. 2026-06-05 22:45 UTCEPSS rescore
  31. 2026-06-05 22:45 UTCEPSS rescore
  32. 2026-06-05 06:08 UTCEPSS rescore
  33. 2026-06-05 06:08 UTCEPSS rescore
  34. 2026-06-04 13:10 UTCEPSS rescore
  35. 2026-06-04 13:10 UTCEPSS rescore
  36. 2026-06-02 20:11 UTCEPSS rescore
  37. 2026-06-02 20:11 UTCEPSS rescore
  38. 2026-06-01 13:50 UTCEPSS rescore
  39. 2026-05-31 22:29 UTCEPSS rescore
  40. 2026-05-31 22:29 UTCEPSS rescore
  41. 2026-05-31 00:15 UTCEPSS rescore
  42. 2026-05-31 00:15 UTCEPSS rescore
  43. 2026-05-29 13:42 UTCEPSS rescore
  44. 2026-05-28 13:43 UTCEPSS rescore
  45. 2026-05-28 13:43 UTCEPSS rescore
  46. 2026-05-27 13:39 UTCEPSS rescore
  47. 2026-05-27 13:39 UTCEPSS rescore
  48. 2026-05-26 17:05 UTCEG score recompute
  49. 2026-05-26 17:05 UTCVendor advisory
  50. 2026-05-26 17:05 UTCGHSA enrichment
  51. 2026-05-26 13:42 UTCEPSS rescore
  52. 2026-05-26 13:42 UTCEPSS rescore
  53. 2026-05-26 13:07 UTCOSV refresh
  54. 2026-05-26 07:17 UTCEPSS rescore
  55. 2026-05-26 07:17 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 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 in the National Vulnerability Database 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 99.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
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?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2020-28018, 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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