Secure Firewall Management CenterApplication · Cisco
CVE-2021-1223
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedMultiple 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 packets and deliver a malicious payload.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThis is a vulnerability in Cisco's Snort detection engine affecting multiple Cisco products. The flaw is in how the Snort engine incorrectly handles HTTP Range headers, allowing an unauthenticated remote attacker to craft specific HTTP packets that bypass configured file policies for HTTP traffic. This enables delivery of malicious payloads that would normally be blocked by file inspection policies.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Secure Firewall Management CenterApplication
= 2.9.14.0= 2.9.15= 2.9.16
Secure Firewall Threat DefenseApplication
< 6.7.0
Ios XeOperating system
< 17.4.1< 2.9.17CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify product and installed versionDetermine which Cisco product is in use (Firepower Threat Defense, Secure Firewall Management Center, IOS XE, or standalone Snort) and retrieve its current software version using the product's CLI (e.g., 'show version' on Cisco devices) or management interfaceAffected if The installed version falls within: Firepower Threat Defense < 6.7.0; Secure Firewall Management Center = 2.9.14.0, 2.9.15, or 2.9.16; IOS XE < 17.4.1; or Snort < 2.9.17
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Verify Snort detection engine is activeConfirm that the Snort inspection engine is enabled and processing traffic. On Cisco Firepower/FTD, use 'show snort statistics' or check the policy configuration to confirm Snort is runningAffected if Snort is actively inspecting HTTP traffic and file policies are applied
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Confirm HTTP file inspection policies existReview the configured inspection policies to determine if HTTP file policies (file blocking, malware inspection) are applied to the traffic. Check the access control or intrusion policy configurationAffected if HTTP file inspection or file blocking policies are configured and Snort is processing HTTP traffic
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Check for anomalous HTTP Range header trafficReview network logs, intrusion events, or traffic captures for HTTP requests with Range headers that may be bypassing normal file inspection. Look for suspicious Range header patterns that could indicate exploitation attemptsAffected if Evidence exists of HTTP Range header manipulation in traffic logs or intrusion events
You are affected if your installed product version is within the vulnerable ranges AND Snort is actively processing HTTP traffic with file inspection policies, because the vulnerability allows bypassing those policies via crafted Range headers.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data2.9.176.7.017.4.1
Apply Cisco patches for affected products; in the interim, implement additional HTTP traffic filtering at network edges and monitor for anomalous HTTP range header patterns.
Fix this in Secure Firewall Management Center
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1223 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-1223 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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