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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_SUSP_Doc_RTF_Externalresource_May22

Detects a suspicious pattern in RTF files which downloads external resources as seen in CVE-2022-30190 / Follina exploitation

Suspicious / huntingSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Tobias Michalski, Christian Burkard
Date
2022-05-30
Modified
2022-05-31
Score / Quality
70 / 85

What this rule detects

Detects a suspicious pattern in RTF files which downloads external resources as seen in CVE-2022-30190 / Follina exploitation

It defines 2 patterns (2 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
susp-doc-rtf-externalresource-may22.yarDetection Rule License 1.1
rule SIGNATURE_BASE_SUSP_Doc_RTF_Externalresource_May22 : CVE_2022_30190 FILE
{
	meta:
		description = "Detects a suspicious pattern in RTF files which downloads external resources as seen in CVE-2022-30190 / Follina exploitation"
		author = "Tobias Michalski, Christian Burkard"
		id = "71bb97e0-ec12-504c-a1f6-25039ac91c86"
		date = "2022-05-30"
		modified = "2022-05-31"
		reference = "https://doublepulsar.com/follina-a-microsoft-office-code-execution-vulnerability-1a47fce5629e"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/gen_doc_follina.yar#L63-L79"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "c841e0c1ff78bf8dade5f573a7452b16a7f447cfc19417704b727684a8f3d3ff"
		score = 70
		quality = 85
		tags = "CVE-2022-30190, FILE"

	strings:
		$s1 = " LINK htmlfile \"http" ascii
		$s2 = ".html!\" " ascii

	condition:
		uint32be( 0 ) == 0x7B5C7274 and filesize < 300KB and all of them
}

Strings (2 patterns)

IdentifierTypeValueModifiers
$s1text" LINK htmlfile \"http"ascii
$s2text".html!\" "ascii

Condition

uint32be( 0 ) == 0x7B5C7274 and filesize < 300KB and all of them

In plain words (Heuristic)

  • The file must start with “{\rt” — an RTF document.
  • The file must be smaller than 300KB (a cheap guard that skips large files).
  • All patterns in the rule must match.

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Drop a file here or click to chooseScanned locally with YARA-X. Files up to 200 MB.

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References

Licence & attribution

Author: Tobias Michalski, Christian Burkard

Source repository: Signature Base (Florian Roth / Nextron) @ 94a1c48d7a

Licence: Detection Rule License 1.1 (repository licence)

Original rule

Mirrored via YARA Forge 20260927, which prefixes rule names with the source and adds normalised meta fields.

Rule id: 71bb97e0-ec12-504c-a1f6-25039ac91c86

Tags:CVE_2022_30190FILE

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