CVE-2026-20053
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 3 VBA feature that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to crash. This vulnerability is due to improper range checking when decompressing VBA data, which is user controlled. An attacker could exploit this vulnerability by sending crafted VBA data to the Snort 3 Detection Engine on the targeted device. A successful exploit could allow the attacker to cause an overflow of heap data, which could cause a DoS condition.
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 vulnerability exists in Snort 3's VBA (Visual Basic for Applications) detection feature across multiple Cisco products. The issue stems from improper range validation during VBA data decompression, where attacker-supplied VBA content lacks sufficient bounds checking. A remote, unauthenticated attacker can send specially crafted VBA packets to trigger a heap overflow in the Snort 3 detection engine, causing a denial of service by crashing the IDS/IPS subsystem.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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
- Changed
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
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 Snort 3 installation and versionRun 'snort3 -V' or 'snort --version' to obtain the installed Snort 3 version numberAffected if The installed version falls within the vulnerable version range for this CVE
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Verify VBA inspection is enabled in Snort configurationExamine Snort 3 configuration files (typically snort.lua or *.rules) for VBA-related preprocessor or inspector settings. Look for keywords such as 'vba', 'vb_script', 'vbscript', or 'visual_basic' under the 'preprocessors' or 'inspectors' section that explicitly enable this featureAffected if The VBA/VBScript inspection feature is enabled in the active Snort 3 configuration
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Check for VBA detection modules loadedRun 'snort3 --list-modules' or review loaded module lists for any active VBA-related detection modules. Also inspect the output of 'snort3 --dump-config' for any VBA inspection parametersAffected if A VBA or Visual Basic detection module is loaded and active in the running Snort 3 instance
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Confirm deployment on affected Cisco productIdentify the host system and verify it is a Cisco product that bundles Snort 3 (such as Cisco Firepower, Cisco Firepower NGIPS, or other Cisco IDS/IPS appliances). Check product model, firmware version, or system documentationAffected if The Snort 3 deployment is part of a Cisco security product known to be affected by this vulnerability
A system is affected if it runs a vulnerable Snort 3 version on an affected Cisco product with the VBA inspection feature explicitly enabled in the configuration.
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 dataApply the vendor-specific patches released by Cisco for affected products. Until patches are available, consider disabling the VBA inspection feature in Snort 3 or implementing network-level filtering to block VBA content from untrusted sources.
- Consultation8.0 h
- Implementation12.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20053 — 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-2026-20053 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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