Gunra Ransomware's Linux Variant Has a Fatal Flaw: time()-Seeded rand() Makes Encrypted Files Recoverable Without Paying

2026-03-12 Break Glass Intelligence

https://intel.breakglass.tech/post/gunra-ransomware-s-linux-variant-has-a-fatal-flaw-time-seeded-rand-makes-encrypted-files-recoverable-without-paying

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Breakglass Intelligence analyzed Gunra ransomware's Linux variant, an 84KB Conti-derived ELF expanded into x86-64, i386, ARM, and Windows builds for enterprise and multi-architecture targeting. The Linux build encrypts files with ChaCha20 and RSA-4096, but derives ChaCha20 key material from musl-libc rand() seeded with time(), allowing responders to brute force likely encryption timestamps for .GNRA files. The malware creates .GNRA files, .keystore key storage, and R3ADM3.txt ransom notes while modifying logs, PAM, Polkit, sudoers policy, cron jobs, init scripts, and Bash startup scripts. Breakglass also maps Tor infrastructure, notes Windows-based Apache/PHP leak-site hosting as an OPSEC weakness, and provides hashes, hidden services, behavioral indicators, YARA/Sigma detections, and recovery guidance.

Indicators of Compromise

Type Value First Seen Last Seen
DOMAIN testexampleabcdefghijklmnop.oni… 2026-03-12 2026-03-12
YARA Gunra_ELF_ChaCha20_PRNG_Weakness 2026-03-12 2026-03-12
YARA Gunra_ELF_Builder_Pattern 2026-03-12 2026-03-12
YARA Gunra_ELF_ChaCha20_PRNG_Weakness 2026-03-12 2026-03-12
HASH 6d59bb6a9874b9b03ce6ab998def5b9… 2025-09-23 2026-03-12
HASH 75cb7eb79a5fa0d388547520c6c452c… 2025-09-23 2026-03-12
HASH eb46dfb4f15000a7d4af040b68e5412… 2025-09-23 2026-03-12
HASH 0909ecc86f8a89831c9c229de91b829… 2025-09-23 2026-03-12
HASH 5677dfad26045e271272bc98be2fd24… 2025-09-23 2026-03-12

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