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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_EXPL_POC_Springcore_0Day_Webshell_Mar22_1

Detects webshell found after SpringCore exploitation attempts POC script

ExploitSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth (Nextron Systems)
Date
2022-03-30
Modified
2023-12-05
Score / Quality
70 / 85

What this rule detects

Detects webshell found after SpringCore exploitation attempts POC script

It defines 3 patterns (3 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
expl-poc-springcore-0day-webshell-mar22-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_EXPL_POC_Springcore_0Day_Webshell_Mar22_1 : FILE
{
	meta:
		description = "Detects webshell found after SpringCore exploitation attempts POC script"
		author = "Florian Roth (Nextron Systems)"
		id = "e7047c98-3c60-5211-9ad5-2bfdfb35d493"
		date = "2022-03-30"
		modified = "2023-12-05"
		reference = "https://twitter.com/vxunderground/status/1509170582469943303"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/expl_spring4shell.yar#L36-L50"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "17282b66899356a6051f0b47a7a3f02265737283d760f2256e03a2b934bb63b8"
		score = 70
		quality = 85
		tags = "FILE"

	strings:
		$x1 = ".getInputStream(); int a = -1; byte[] b = new byte[2048];"
		$x2 = "if(\"j\".equals(request.getParameter(\"pwd\")"
		$x3 = ".getRuntime().exec(request.getParameter(\"cmd\")).getInputStream();"

	condition:
		filesize < 200KB and 1 of them
}

Strings (3 patterns)

IdentifierTypeValueModifiers
$x1text".getInputStream(); int a = -1; byte[] b = new byte[2048];"
$x2text"if(\"j\".equals(request.getParameter(\"pwd\")"
$x3text".getRuntime().exec(request.getParameter(\"cmd\")).getInputStream();"

Condition

filesize < 200KB and 1 of them

In plain words (Heuristic)

  • The file must be smaller than 200KB (a cheap guard that skips large files).
  • At least 1 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: Florian Roth (Nextron Systems)

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: e7047c98-3c60-5211-9ad5-2bfdfb35d493

Tags:FILE

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