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How the CVE Works:
CVE-2024-2961 affects Cloudflare’s CIRCL library, specifically its FourQ elliptic curve implementation. The vulnerability arises from insufficient validation of low-order points during Diffie-Hellman (DH) key exchange. Attackers can inject a maliciously crafted low-order point, forcing the shared secret to become the identity element (zero). This breaks forward secrecy and allows passive decryption of sessions.
Additionally, `ScalarMult` incorrectly validates curve points, leading to faulty outputs in `isEqual` checks. This may result in false positives when verifying whether a point lies on FourQ, enabling further cryptographic manipulation. The flaw stems from missing checks in the point decompression and multiplication logic, allowing invalid curve attacks (ICA).
DailyCVE Form:
Platform: Cloudflare CIRCL
Version: <1.6.1
Vulnerability: Low-order point injection
Severity: Critical
Date: 2024-04-15
Prediction: Patch expected by 2024-04-30
What Undercode Say:
Analytics:
- Exploit requires MITM positioning or malicious peer in DH.
- Impacts TLS/SSH implementations using FourQ.
- CVSS 9.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N).
Exploit Commands:
1. Capture handshake:
openssl s_client -connect target:443 -named_curve fourq
2. Forge low-order point:
mal_point = b'\x00' 32 Zero point
Protection Code:
1. Upgrade CIRCL:
go get github.com/cloudflare/[email protected]
2. Validate points pre-multiplication:
func SafeScalarMult(point []byte) bool {
if !isOnCurve(point) { return false }
return true
}
Mitigations:
- Disable FourQ in TLS prior to patching.
- Audit logs for repeated handshake failures.
- Enforce ephemeral key rotation.
References:
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
