Rustls CVEs and Security Vulnerabilities

CVE-2026-123610

rustls before 0.23.46 Denial of Service via Brotli Certificate Decompression

rustls before 0.23.46 contains an uncontrolled memory allocation flaw in its optional Brotli certificate decompression, which limits decompressed output size but accepts an input-selected large history window. Malicious peers can send a certificate with a five-byte Brotli header requesting up to 1 GiB before authentication, aborting Brotli-enabled clients or client-authenticating servers whose allocator cannot satisfy the request.

CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed

Vendors

Rustls Rustls Project

Products

Rustls Rustls

CVE-2026-123611

rustls before 0.23.46 Key Exchange Downgrade via Unauthenticated ServerHello

rustls before 0.23.46 contains a key exchange downgrade vulnerability that allows network attackers to poison the per-server-name key-exchange group record via an unauthenticated ServerHello. Attackers can answer one connection with a ServerHello selecting X25519, causing later ClientHellos to send only classical shares and lose post-quantum confidentiality.