PatchTheCVECVE-2021-1236: Multiple Cisco products are affected by a vulnerability in the Snort application detection engine that could a
CVE-2021-1236 is a medium-severity flaw (CVSS 5.3) affecting ios xe, secure firewall management center, secure firewall threat defense. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Multiple Cisco products are affected by a vulnerability in the Snort application detection engine that could allow an unauthenticated, remote attacker to bypass the configured policies on an affected system. The vulnerability is due to a flaw in the detection algorithm. An attacker could exploit this vulnerability by sending crafted packets that would flow through an affected system. A successful exploit could allow the attacker to bypass the con
Why this priority
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 2.2% (top 18%) |
| CISA exploited list | No |
| Weakness | CWE-670 |
| Published | 2021-01-13 |
| Last modified | 2026-08-11 |
Last updated 2026-08-11 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-1236?
ios xe: upgrade to 17.4.1; secure firewall management center: downgrade or apply the listed mitigation; secure firewall threat defense: upgrade to 6.5.0.5. Exact commands for each OS are on this page.
Is CVE-2021-1236 being exploited?
CVE-2021-1236 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-1236 affect?
CVE-2021-1236 affects ios xe, secure firewall management center, secure firewall threat defense. Severity is medium (CVSS 5.3). Multiple Cisco products are affected by a vulnerability in the Snort application detection engine that could allow an unauthenticated, remote attacker to bypass the configured policies on an affected system. The vulnerability is due to a fl
How urgent is CVE-2021-1236?
Priority 44/100. Remotely exploitable, no login, no user action
Software pages
iOS vulnerabilities · Cisco IOS XE vulnerabilities · Cisco vulnerabilities · Suricata and Snort vulnerabilities
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