PatchTheCVECVE-2021-1223: Multiple Cisco products are affected by a vulnerability in the Snort detection engine that could allow an unau
CVE-2021-1223 is a high-severity flaw (CVSS 7.5) affecting secure firewall management center, secure firewall threat defense, ios xe. 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 detection engine that could allow an unauthenticated, remote attacker to bypass a configured file policy for HTTP. The vulnerability is due to incorrect handling of an HTTP range header. An attacker could exploit this vulnerability by sending crafted HTTP packets through an affected device. A successful exploit could allow the attacker to bypass configured file policy for HTTP p
Why this priority
- High severity
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 2.0% (top 19%) |
| CISA exploited list | No |
| Weakness | CWE-693 |
| 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-2021-1223?
secure firewall management center: downgrade or apply the listed mitigation; secure firewall threat defense: upgrade to 6.7.0; ios xe: upgrade to 17.4.1. Exact commands for each OS are on this page.
Is CVE-2021-1223 being exploited?
CVE-2021-1223 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-2021-1223 affect?
CVE-2021-1223 affects secure firewall management center, secure firewall threat defense, ios xe. Severity is high (CVSS 7.5). Multiple Cisco products are affected by a vulnerability in the Snort detection engine that could allow an unauthenticated, remote attacker to bypass a configured file policy for HTTP. The vulnerability is due to incorrect handling of an HTT
How urgent is CVE-2021-1223?
Priority 51/100. High severity; Remotely exploitable, no login, no user action
Software pages
iOS vulnerabilities · Cisco IOS XE vulnerabilities · Cisco vulnerabilities · Suricata and Snort vulnerabilities
Related CVEs
- CVE-2026-20316 MEDIUM 5.3 EXPLOITED UPGRADE Cisco Secure Firewall Management Center Use of Hard-coded Password Vulnerability
- CVE-2026-20079 CRITICAL 10.0 EXPLOITED DOWNGRADE Cisco Firewall Management Center Authentication Bypass Using an Alternate Path or Channel Vulnerability
- CVE-2026-20044 MEDIUM 6.0 UPGRADE A vulnerability in the lockdown mechanism of Cisco Secure Firewall Management Center (FMC) Software could allo
- CVE-2019-1978 MEDIUM 5.8 MITIGATE UPGRADE A vulnerability in the stream reassembly component of Cisco Firepower Threat Defense Software, Cisco FirePOWER
- CVE-2021-40114 MEDIUM 6.8 DOWNGRADE UPGRADE Multiple Cisco products are affected by a vulnerability in the way the Snort detection engine processes ICMP t