| Titolo | PuTTY Project (Simon Tatham) PuTTY 0.83 Improper Verification of Cryptographic Signature |
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| Descrizione | PuTTY's Ed25519 verification logic in crypto/ecc-ssh.c (eddsa_verify) does not enforce strict canonical-scalar validation (S < L). Because of this, a valid signature (R, S) can be malleated into (R, S+L) and still pass verification.
Using the provided PoC with PuTTY testcrypt (ssh_key_verify), both signatures verify successfully:
putty verify(orig) = True
putty verify(S+L) = True
This demonstrates Ed25519 signature malleability acceptance (non-canonical signature accepted). Historically, similar signature malleability vulnerabilities have been discovered and assigned CVEs in other projects, including CVE-2026-3706, CVE-2020-36843, and CVE-2024-45193. |
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| Fonte | ⚠️ https://github.com/py-thok/putty-ed25519-malleability-s-plus-l |
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| Utente | pythok (UID 95793) |
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| Sottomissione | 09/03/2026 07:40 (7 mesi fa) |
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| Moderazione | 22/03/2026 12:48 (13 days later) |
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| Stato | Accettato |
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| Voce VulDB | 352429 [PuTTY 0.83 Ed25519 Signature crypto/ecc-ssh.c eddsa_verify autenticazione debole] |
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| Punti | 20 |
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