Attachment: CVE-2023-21716 - Microsoft Office Remote Code Execution Vulnerability

calendar Dec 19, 2023  ยท
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Attachment contains an RTF file with a font table defining an excessive number of fonts, used to exploit CVE-2023-21716.

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 1name: "Attachment: CVE-2023-21716 - Microsoft Office Remote Code Execution Vulnerability"
 2description: |
 3    Attachment contains an RTF file with a font table defining an excessive number of fonts, used to exploit CVE-2023-21716.
 4references:
 5  - "https://delivr.to/payloads?id=0a465e03-82a7-42c1-9ded-b0b6b046c86d"
 6  - "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21716"
 7  - "https://twitter.com/jduck/status/1632471544935923712"
 8  - "https://github.com/gyaansastra/CVE-2023-21716"
 9type: "rule"
10severity: "high"
11source: |
12  type.inbound
13  and any(attachments,
14          (
15            .file_extension in~ ("rtf", "doc", "docx")
16            or .file_extension in~ $file_extensions_common_archives
17            or .file_extension in~ $file_extensions_macros
18            or (
19                .file_extension is null
20                and .file_type == "unknown"
21                and .content_type == "application/octet-stream"
22                and .size < 100000000
23            )
24          )
25          and any(file.explode(.),
26                  any(.scan.strings.strings, strings.ilike(., '*\fonttbl*'))
27                  and length(filter(.scan.strings.strings, strings.ilike(., '{\f*;}'))) > 10000
28          )
29  )  
30attack_types:
31  - "Malware/Ransomware"
32tactics_and_techniques:
33  - "Exploit"
34detection_methods:
35  - "Content analysis"
36  - "File analysis"
37id: "23714cca-f0c6-5fa5-a68b-98c9d60a508d"
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