CVE-2021-34697

MEDIUMNVD 5.85.8—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.8 under NVD CVSS v3. EPSS exploit probability: 1.3%, top 32% 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
5.8
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 5.8Exploit: NoneExposed: 0

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

A vulnerability in the Protection Against Distributed Denial of Service Attacks feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to conduct denial of service (DoS) attacks to or through the affected device. This vulnerability is due to incorrect programming of the half-opened connections limit, TCP SYN flood limit, or TCP SYN cookie features when the features are configured in vulnerable releases of Cisco IOS XE Software. An attacker could exploit this vulnerability by attempting to flood traffic to or through the affected device. A successful exploit could allow the attacker to initiate a DoS attack to or through an affected device.

CVSS v3
5.8
EG Score
5.8(medium)
EG Risk
42(Track)
EG Risk 42/100SSVC: 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
Severity58% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
68.0%
KEV
Not listed

Published

September 23, 2021

Last Modified

November 21, 2024

References (2)

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.

  1. 2026-07-23 02:01 UTCEG score recompute
  2. 2026-07-22 22:48 UTCEG score recompute
  3. 2026-07-22 14:06 UTCEPSS rescore
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  71. 2026-05-26 10:01 UTCGHSA enrichment
  72. 2026-05-26 07:17 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2021-34697?
CVE-2021-34697 is a medium vulnerability published on September 23, 2021. A vulnerability in the Protection Against Distributed Denial of Service Attacks feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to conduct denial of service (DoS) attacks to or through the affected device. This vulnerability is due to incorrect programming of the…
When was CVE-2021-34697 disclosed?
CVE-2021-34697 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-2021-34697 actively exploited?
CVE-2021-34697 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 68.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-34697?
CVE-2021-34697 has a CVSS v3 base score of 5.8 (NVD).
How do I remediate CVE-2021-34697?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-34697, 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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