CVE-2021-1288: Cisco IOS XR Software Enf Broker Denial of Service Vulnerability
Telemetry drift only. No threshold crossed and no authority ruling changed.
CVE record, CISA KEV and EPSS as of 2026-10-18.
CVEs like this one computed, by meaning
What to do now held facts and links
- Upgrade to the fixed version for your release line, or later: ios xr 5.2.6; ios xr 5.3.4; ios xr 6.0.2 upper bounds of the CVE record's affected ranges
- Record your decision, dated and frozen with today's evidence: patch by a date · mitigated by a compensating control · deferred · accepted the risk · not affected
- Check your version against the ranges this record publishes.
What it is stated by the CNA
Multiple vulnerabilities in the ingress packet processing function of Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. For more information about these vulnerabilities, see the Details section of this advisory.
- weakness
- CWE-399
- affected
- Cisco IOS XR Software
- published ranges
- cisco ios xr >= 5.0.0 < 5.2.6; cisco ios xr >= 5.3.0 < 5.3.4; cisco ios xr >= 6.0.0 < 6.0.2
- first unaffected version, by branch
- ios xr 5.2.6; ios xr 5.3.4; ios xr 6.0.2
- severity
- 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
- assigned by
- cisco
- published
- 2021-02-04
check us tools.cisco.com
Exploit code held, dated
- exploit code
- None held in the PoC-in-GitHub feed. A public repository changes this brief.
What moved held, dated
| date | EPSS | event |
|---|---|---|
| 14 Apr 2021 | 0.00651 | |
| 6 Jan 2022 | 0.02857 | |
| 4 Feb 2022 | 0.04499 | |
| 1 Apr 2022 | 0.01055 | |
| 7 Mar 2023 | 0.00137 | scoring model v2023.03.01 |
| 11 Sep 2023 | 0.0014 | |
| 21 Oct 2023 | 0.00159 | |
| 17 Mar 2025 | 0.00651 | scoring model v2025.03.14 |
| 19 Mar 2025 | 0.00763 | |
| 25 Mar 2025 | 0.00991 | |
| 29 Mar 2025 | 0.01345 | |
| 30 Mar 2025 | 0.00991 | |
| 28 Apr 2025 | 0.00596 | |
| 15 Jun 2026 | 0.01952 | scoring model v2026.06.15 |
14 observations held. A step marked with a scoring model moved because the measurement was replaced, not because the vulnerability changed.
Outside the record researched, cited
This section reads the record's references and adds cited findings from outside it. It needs an account. Everything above is held facts and is complete without it.
What would change this brief held, dated
- CISA KEV
- Not listed in the catalogue we hold. A listing changes this brief.
- exploit probability
- 0.02 on 2026-06-15 (FIRST's EPSS, a probability and not evidence of exploitation). Next band line: 10% (0.10). Crossing a line changes this brief.
- fix
- Held: ios xr 5.2.6; ios xr 5.3.4; ios xr 6.0.2. A newer fix from the CNA or OSV changes this brief.
How to check this
Every value above is held with two dates: when it was true upstream (as_of) and when we recorded it (tx_from). Re-derive the exploit probability as it stood on any date:
SELECT value, source, source_version, as_of, tx_from
FROM volatile_valid_as_of('CVE-2021-1288', '2026-10-30T23:59:59.999999Z', now());