CVE intelligence and bounded remediation

CVE-2023-26430 — Attackers with access to user accounts can inject arbitrary control characters to SIEVE mail-filter rules

Medium CVSS 4.3

Attackers with access to user accounts can inject arbitrary control characters to SIEVE mail-filter rules. This could be abused to access SIEVE extension that are not allowed by App Suite or to inject rules which would break per-user filter processing, requiring manual cleanup of such rules. We have added sanitization to all mail-filter APIs to avoid forwardning control characters to subsystems. No publicly available exploits are known.

Severity
Medium
CVSS
4.3 (3.1)
Published
2023-08-02
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-77

Affected products

  • open-xchange / open-xchange_appsuite_backend / 7.10.6
  • open-xchange / open-xchange_appsuite_backend / 8.10.0

Matched remediation archetype

Command, code, expression, and template injection

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Check exposure

  • Trace untrusted values to process execution, interpreters, evaluators, template engines, dynamic imports, and administrative scripting features.
  • Determine whether the affected path is reachable across each trust boundary and which service account or host privilege it inherits.
  • Review configuration for optional execution features, unsafe compatibility modes, and shell invocation.

Remediate safely

  • Replace string-built commands or evaluated code with fixed operations and structured argument APIs that do not invoke a shell.
  • Use strict allowlists for operation identifiers and reject unexpected input before it reaches any interpreter.
  • Update the affected component and add inert regression tests covering metacharacters, encoding variants, and alternate request paths.

Authoritative sources

Complete CVE record and remediation plan

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