CVE-2019-18420

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

Score 6.5 from GitHub Security Advisory published 2022-05-24. NVD baseline CVSS 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
6.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 3%CVSS: 6.5Exploit: NoneExposed: 0

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

An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to cause a denial of service via a VCPUOP_initialise hypercall. hypercall_create_continuation() is a variadic function which uses a printf-like format string to interpret its parameters. Error handling for a bad format character was done using BUG(), which crashes Xen. One path, via the VCPUOP_initialise hypercall, has a bad format character. The BUG() can be hit if VCPUOP_initialise executes for a sufficiently long period of time for a continuation to be created. Malicious guests may cause a hypervisor crash, resulting in a Denial of Service (DoS). Xen versions 4.6 and newer are vulnerable. Xen versions 4.5 and earlier are not vulnerable. Only x86 PV guests can exploit the vulnerability. HVM and PVH guests, and guests on ARM systems, cannot exploit the vulnerability.

CVSS v3
6.5
EG Score
6.5(medium)
EPSS
83.0%
KEV
Not listed

Published

October 31, 2019

Last Modified

November 21, 2024

References (18)

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 41× 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. 2026-07-11 08:24 UTCEPSS rescore
  2. 2026-07-11 08:24 UTCEPSS rescore
  3. 2026-07-09 19:06 UTCEPSS rescore
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  10. 2026-07-04 06:28 UTCEPSS rescore
  11. 2026-07-02 17:56 UTCOSV refresh
  12. 2026-07-01 15:03 UTCEPSS rescore
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  14. 2026-06-30 23:20 UTCEPSS rescore
  15. 2026-06-29 14:03 UTCEPSS rescore
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  1. 2026-06-22 14:23 UTCEPSS rescore
  2. 2026-06-21 14:54 UTCEPSS rescore
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  4. 2026-06-21 01:57 UTCEPSS rescore
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  6. 2026-06-19 19:23 UTCEPSS rescore
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  8. 2026-06-18 17:50 UTCEPSS rescore
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  11. 2026-06-15 17:45 UTCEPSS rescore
  12. 2026-06-14 23:15 UTCEPSS rescore
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  14. 2026-06-14 15:43 UTCOSV refresh
  15. 2026-06-13 22:58 UTCEPSS rescore
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  17. 2026-06-11 13:58 UTCEPSS rescore
  18. 2026-06-10 22:16 UTCEPSS rescore
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  20. 2026-06-07 15:23 UTCEPSS rescore
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  22. 2026-06-06 13:45 UTCEPSS rescore
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  24. 2026-06-05 22:45 UTCEPSS rescore
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  38. 2026-05-29 13:42 UTCEPSS rescore
  39. 2026-05-28 13:43 UTCEPSS rescore
  40. 2026-05-27 13:38 UTCEPSS rescore
  41. 2026-05-27 12:24 UTCEG score recompute
  42. 2026-05-27 12:24 UTCGHSA enrichment
  43. 2026-05-26 13:42 UTCEPSS rescore
  44. 2026-05-26 13:42 UTCEPSS rescore
  45. 2026-05-26 07:17 UTCEPSS rescore
  46. 2026-05-26 07:17 UTCEPSS rescore
  47. 2026-05-26 07:17 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2019-18420?
CVE-2019-18420 is a medium vulnerability published on October 31, 2019. An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to cause a denial of service via a VCPUOPinitialise hypercall. hypercallcreatecontinuation() is a variadic function which uses a printf-like format string to interpret its parameters. Error handling for a bad format…
When was CVE-2019-18420 disclosed?
CVE-2019-18420 was first published in the National Vulnerability Database on October 31, 2019, 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-2019-18420 actively exploited?
CVE-2019-18420 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 83.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2019-18420?
CVE-2019-18420 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2019-18420?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2019-18420, 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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