nginx accepts SHA-224 signature algorithms in TLS 1.2
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On Cloudron 9.2.0 (nginx 1.24.0, OpenSSL 3.0.13) the generated vhosts pin ssl_protocols and ship a curated ssl_ciphers list, but the TLS 1.2 signature algorithms are left at OpenSSL's defaults, which still include the SHA-224 variants. A client offering nothing but ECDSA+SHA224 gets a completed handshake with Peer signature type: ecdsa_sha224.
https://en.internet.nl flags this under "Hash function for key exchange" as phase out, following the NCSC TLS guidelines 2025-05 §3.3.5, and notes it will likely be rated insufficient in a future update. It's the only remaining recommendation on an otherwise 100% site, and it sits in the platform's nginx configuration rather than anywhere an app or admin can reach.
Since v10 is in the works — would this be worth picking up along the way?
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G girish marked this topic as a regular topic
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Since we don't set SignatureAlgorithms, the default comes from OpenSSL. It's there even in Ubuntu 26, OpenSSL 3.5.5 (27 Jan 2026).
It's not a real security issue to have SHA-224 listed since preference is mostly client driven. Most of the modern servers will have SHA-256 (or PSS, never heard of that before I researched this).
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G girish marked this topic as a question
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G girish has marked this topic as solved
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Fair enough — you're right that it isn't exploitable. The client sends signature_algorithms and the server picks from the intersection, so nothing modern ends up on SHA-224 unless it explicitly asks for it, which is exactly what my test did.
Where it still bites is compliance rather than security: organisations measured against the NCSC guidelines get it reported on every scan, and internet.nl states they expect to reclassify it from phase out to insufficient in a future update — at which point it stops being a recommendation and becomes a failed subtest. That's the only thing that really changes the calculus, and whether it's worth pre-empting is your call.
Same algorithm turns up on the mail server for the same reason, which is in the other thread.
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