CVE-2021-34727

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-24. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 3%CVSS: 9.8Exploit: NoneExposed: 0

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

A vulnerability in the vDaemon process in Cisco IOS XE SD-WAN Software could allow an unauthenticated, remote attacker to cause a buffer overflow on an affected device. This vulnerability is due to insufficient bounds checking when an affected device processes traffic. An attacker could exploit this vulnerability by sending crafted traffic to the device. A successful exploit could allow the attacker to cause a buffer overflow and possibly execute arbitrary commands with root-level privileges, or cause the device to reload, which could result in a denial of service condition.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
60(Track)
EG Risk 60/100SSVC: 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%
Exploitation3% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
83.9%
KEV
Not listed

Published

September 23, 2021

Last Modified

November 21, 2024

Advisory Details (1)

Auto-updated Jul 1, 2026
No patch confirmed yet.
generic

Cisco IOS XE SD-WAN Software Buffer Overflow Vulnerability

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxesdwan-rbuffover-vE2OB6tp

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 45× 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 101 total refreshes for this CVE.

  1. 2026-07-23 14:16 UTCEPSS rescore
  2. 2026-07-23 14:16 UTCEPSS rescore
  3. 2026-07-23 02:01 UTCEG score recompute
  4. 2026-07-22 22:48 UTCEG score recompute
  5. 2026-07-22 14:06 UTCEPSS rescore
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  7. 2026-07-21 15:22 UTCEPSS rescore
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  25. 2026-07-09 19:07 UTCEPSS rescore
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  1. 2026-07-08 15:12 UTCEPSS rescore
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  3. 2026-07-06 16:25 UTCEPSS rescore
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  21. 2026-06-23 21:31 UTCEPSS rescore
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  23. 2026-06-22 14:24 UTCEPSS rescore
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  25. 2026-06-21 14:55 UTCEPSS rescore
  26. 2026-06-21 01:58 UTCEPSS rescore
  27. 2026-06-21 01:58 UTCEPSS rescore
  28. 2026-06-19 19:24 UTCEPSS rescore
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  30. 2026-06-18 17:51 UTCEPSS rescore
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  35. 2026-06-15 17:46 UTCEPSS rescore
  36. 2026-06-14 23:15 UTCEPSS rescore
  37. 2026-06-13 22:58 UTCEPSS rescore
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  39. 2026-06-12 23:10 UTCEPSS rescore
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  41. 2026-06-11 13:58 UTCEPSS rescore
  42. 2026-06-10 22:16 UTCEPSS rescore
  43. 2026-06-10 13:20 UTCEPSS rescore
  44. 2026-06-08 14:15 UTCEPSS rescore
  45. 2026-06-08 14:15 UTCEPSS rescore
  46. 2026-06-07 15:23 UTCEPSS rescore
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  48. 2026-06-06 13:46 UTCEPSS rescore
  49. 2026-06-06 13:46 UTCEPSS rescore
  50. 2026-06-06 13:46 UTCEPSS rescore
  51. 2026-06-05 22:45 UTCEPSS rescore
  52. 2026-06-05 06:09 UTCEPSS rescore
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  54. 2026-06-04 13:10 UTCEPSS rescore
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  56. 2026-06-02 20:11 UTCEPSS rescore
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  58. 2026-06-01 13:50 UTCEPSS rescore
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  60. 2026-05-31 22:29 UTCEPSS rescore
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  68. 2026-05-27 13:39 UTCEPSS rescore
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  71. 2026-05-26 13:42 UTCEPSS rescore
  72. 2026-05-26 10:01 UTCEG score recompute
  73. 2026-05-26 10:01 UTCGHSA enrichment
  74. 2026-05-26 07:17 UTCEPSS rescore
  75. 2026-05-26 07:17 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-34727?
CVE-2021-34727 is a critical vulnerability published on September 23, 2021. A vulnerability in the vDaemon process in Cisco IOS XE SD-WAN Software could allow an unauthenticated, remote attacker to cause a buffer overflow on an affected device. This vulnerability is due to insufficient bounds checking when an affected device processes traffic. An attacker could exploit…
When was CVE-2021-34727 disclosed?
CVE-2021-34727 was first published in the National Vulnerability Database on September 23, 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-2021-34727 actively exploited?
CVE-2021-34727 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 83.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-34727?
CVE-2021-34727 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-34727?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-34727, 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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