CVE-2026-23920
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 · uneditedHost and event action script input is validated with a regex (set by the administrator), but the validation runs in multiline mode. If ^ and $ anchors are used in user input validation, an injected newline lets authenticated users bypass the check and inject shell commands.
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 confidenceThe vulnerability stems from host and event action script input validation using administrator-defined regex running in multiline mode. When ^ and $ anchors are used in multiline mode, they match the start and end of any line rather than the entire string. By injecting a newline character into the input, an authenticated user can bypass the regex validation intended to prevent shell command injection, allowing arbitrary shell commands to be executed.
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
- Low
- Authentication
- X
- User interaction
- None
- Scope
- X
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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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Locate regex validation configurations for host/event action scriptsSearch configuration files and code for patterns using regex validation related to host or event action scripts. Look for keywords like 'regex', 'validation', 'action', 'script', 'host'.Affected if Regex validation is defined for host or event action script inputs in the environment
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Identify if multiline mode is enabled for regex patternsExamine the regex definitions or code that uses them. Look for multiline flags (/m in many languages, or Pattern.MULTILINE, re.MULTILINE) or multiline mode configuration.Affected if The regex validation runs in multiline mode, causing ^ and $ to match line boundaries instead of string boundaries
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Check for use of ^ and $ anchors in security-critical regexReview the identified regex patterns for the presence of ^ (caret) and $ (dollar) anchors in patterns intended to prevent command injection or validate script input.Affected if Security-critical regex validation uses ^ and $ anchors which, in multiline mode, can be bypassed with newline injection
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Verify input handling allows newline characters in validated fieldsTest or inspect the input validation logic to determine whether newline characters (\n, \r\n) can be passed through the validated input fields for host or event action scripts.Affected if Newline characters can be injected into input fields that undergo regex validation, enabling the anchor bypass
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Confirm authenticated users can provide input to these validation fieldsReview access controls and input paths to determine if authenticated users (non-administrators) can submit input to the regex-validated host or event action script fields.Affected if Authenticated users can supply input to the vulnerable validation fields, enabling the bypass attack
A user is affected if their environment uses regex validation with multiline mode for host or event action script input, where ^ and $ anchors can be bypassed by injecting newline characters into the validated fields.
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 dataReplace ^ and $ regex anchors with \A (start of string) and \z (end of string) anchors respectively, or disable multiline mode for security-critical validation to prevent newline injection bypass.
- Consultation2.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-23920 — 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-2026-23920 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
- No weaponised exploit code, or anything meant to cause harm
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