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SEKOIA_Exploit_Linux_Eop_Cve202121974_Exploit_Strings

Detects CVE-2021-21974 Local Privesc exploit

ExploitSEKOIA.IO CommunityDetection Rule License 1.1Compiles with YARA-X
Author
Sekoia.io
Date
2023-12-08
Modified
2024-12-19
Score / Quality
75 / 80

What this rule detects

Detects CVE-2021-21974 Local Privesc exploit

Targets: Linux ELF.

It defines 4 patterns (4 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
exploit-linux-eop-cve202121974-exploit-strings.yarDetection Rule License 1.1
rule SEKOIA_Exploit_Linux_Eop_Cve202121974_Exploit_Strings : CVE_2021_21974 FILE
{
	meta:
		description = "Detects CVE-2021-21974 Local Privesc exploit"
		author = "Sekoia.io"
		id = "8e1fbbe5-7d51-48b4-80d5-90abff8cab9e"
		date = "2023-12-08"
		modified = "2024-12-19"
		reference = "https://github.com/SEKOIA-IO/Community"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/exploit_linux_eop_cve202121974_exploit_strings.yar#L1-L18"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "a2e6e2660fcbf6ffa80809c02ca78fae85d27f6cd8d2c83bb2645a86124ca7f2"
		score = 75
		quality = 80
		tags = "CVE-2021-21974, FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$ = ".name.replace('Thread','SLP Client'"
		$ = "print('[' + name + '] recv: ', d)"
		$ = "requests[28].put(connect())"
		$ = "[+] stack enviorn address:"

	condition:
		uint32be( 0 ) == 0x7f454c46 and filesize < 1MB and all of them
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$text".name.replace('Thread','SLP Client'"
$text"print('[' + name + '] recv: ', d)"
$text"requests[28].put(connect())"
$text"[+] stack enviorn address:"

Condition

uint32be( 0 ) == 0x7f454c46 and filesize < 1MB and all of them

In plain words (Heuristic)

  • The file must start with the ELF header — a Linux/Unix executable.
  • The file must be smaller than 1MB (a cheap guard that skips large files).
  • All patterns in the rule must match.

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References

Licence & attribution

Author: Sekoia.io

Source repository: SEKOIA.IO Community @ a438a5901a

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: 8e1fbbe5-7d51-48b4-80d5-90abff8cab9e

Metadata

version1.0
classificationTLP:CLEAR

Tags:CVE_2021_21974FILE

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