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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_HKTL_EXPL_POC_NET_Sharepoint_CVE_2023_29357_Sep23_1

Detects a C# POC to exploit CVE-2023-29357 on Microsoft SharePoint servers

Hack toolSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth
Date
2023-10-01
Modified
2023-12-05
Score / Quality
80 / 85

What this rule detects

Detects a C# POC to exploit CVE-2023-29357 on Microsoft SharePoint servers

Targets: Windows PE.

It defines 8 patterns (8 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

hktl-expl-poc-net-sharepoint-cve-2023-29357-sep23-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_HKTL_EXPL_POC_NET_Sharepoint_CVE_2023_29357_Sep23_1 : CVE_2023_29357 FILE
{
	meta:
		description = "Detects a C# POC to exploit CVE-2023-29357 on Microsoft SharePoint servers"
		author = "Florian Roth"
		id = "aa6aeb00-b162-538c-a670-cbff525dd8f1"
		date = "2023-10-01"
		modified = "2023-12-05"
		reference = "https://github.com/LuemmelSec/CVE-2023-29357"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/expl_sharepoint_cve_2023_29357.yar#L37-L62"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "cf621cc9c5074f531df61623b09db68478e94ae6a9a7acc26aa8d9dde79bd30c"
		score = 80
		quality = 85
		tags = "CVE-2023-29357, FILE"

	strings:
		$x1 = "{f22d2de0-606b-4d16-98d5-421f3f1ba8bc}" ascii wide
		$x2 = "{F22D2DE0-606B-4D16-98D5-421F3F1BA8BC}" ascii wide
		$s1 = "Bearer"
		$s2 = "hashedprooftoken"
		$s3 = "/_api/web/"
		$s4 = "X-PROOF_TOKEN"
		$s5 = "00000003-0000-0ff1-ce00-000000000000"
		$s6 = "IsSiteAdmin"

	condition:
		uint16( 0 ) == 0x5a4d and filesize < 800KB and ( 1 of ( $x* ) or all of ( $s* ) )
}

Strings (8 patterns)

IdentifierTypeValueModifiers
$x1text"{f22d2de0-606b-4d16-98d5-421f3f1ba8bc}"ascii wide
$x2text"{F22D2DE0-606B-4D16-98D5-421F3F1BA8BC}"ascii wide
$s1text"Bearer"
$s2text"hashedprooftoken"
$s3text"/_api/web/"
$s4text"X-PROOF_TOKEN"
$s5text"00000003-0000-0ff1-ce00-000000000000"
$s6text"IsSiteAdmin"

Condition

uint16( 0 ) == 0x5a4d and filesize < 800KB and ( 1 of ( $x* ) or all of ( $s* ) )

In plain words (Heuristic)

  • The file must start with “MZ” — a Windows executable (PE).
  • The file must be smaller than 800KB (a cheap guard that skips large files).
  • All patterns in ( $s* ) must match.
  • At least 1 patterns in ( $x* ) must match.

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References

Licence & attribution

Author: Florian Roth

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: aa6aeb00-b162-538c-a670-cbff525dd8f1

Tags:CVE_2023_29357FILE