NGINX Post-Quantum TLS: X25519MLKEM768 with OpenSSL 3.5
by Danila Vershinin, September 20, 2026
Technical Briefing: NGINX Post-Quantum TLS — X25519MLKEM768 with OpenSSL 3.5 The Problem: Harvest Now, Decrypt Later The threat model is not a quantum computer breaking TLS today — it is an attacker recording encrypted traffic now and decrypting it once a cryptographically relevant quantum computer exists. Session cookies expire in hours, but health records, contracts, source trees, and private keys remain sensitive for a decade or more. The precise vulnerability matters: Shor’s algorithm break…
Read More... Parallel ESI for Varnish 6.0 LTS: vmod-pesi Now Packaged
by Danila Vershinin, September 19, 2026
Technical Briefing: Parallel ESI for Varnish 6.0 LTS via vmod-pesi The Problem: Sequential ESI Fragment Assembly Stock open-source Varnish processes ESI includes sequentially. A page containing two uncached fragments that each take 2 seconds to render therefore takes over 4 seconds to assemble — the total is the sum of fragment latencies, not the maximum. This is a structural limitation of the open-source daemon, not a configuration issue. The Implementation: A Backport of libvdp-pesi GetPageSp…
Read More... NGINX QUIC reuseport: HTTP/3 Silently Breaks Without It
by Danila Vershinin, September 18, 2026
Technical Briefing: NGINX HTTP/3 reuseport, quicbpf, and SELinux The Problem: HTTP/3 Silently Fails Without reuseport With workerprocesses greater than 1, a QUIC listener configured without reuseport shares a single UDP socket across all workers. Because QUIC has no accept() step, every datagram arrives on that one socket, and whichever worker wakes first grabs it — even if it does not own that connection. The owning worker then receives mid-connection datagrams it cannot handle, producing H3RE…
Read More... NGINX Certificate Compression: RFC 8879 for Every Browser
by Danila Vershinin, September 15, 2026
Technical Briefing: RFC 8879 Certificate Compression in NGINX Problem Statement The TLS 1.3 certificate chain dominates the server’s first flight and competes with the initial congestion window and QUIC’s 3x amplification limit. RFC 8879 certificate compression shrinks that chain on every fresh handshake — a tested production chain dropped from 4735 to 3750 bytes (20.8% saving). NGINX supports this via a single directive: nginx sslcertificatecompression on; It is valid in http, server, and stre…
Read More... Post-Quantum NGINX: OpenSSL 3.5 on Debian and Ubuntu
by Danila Vershinin, September 14, 2026
Technical Briefing: Post-Quantum NGINX with OpenSSL 3.5 on Debian and Ubuntu Problem Statement NGINX packages on Debian and Ubuntu previously linked against each distribution’s system OpenSSL. On Ubuntu 20.04 (focal), that meant OpenSSL 1.1.1, which reached upstream end-of-life on 11 September 2023. This also constrained which TLS features were available depending on the suite, and left DEB and RPM builds as separate stacks. Implementation NGINX packages on Debian and Ubuntu now link against an…
Read More... OpenSSL 4.0 for NGINX: Why We Ship 3.5 LTS Instead
by Danila Vershinin,
Technical Briefing: OpenSSL 3.5 LTS vs. 4.0 for NGINX Packaging Problem Statement The decision between OpenSSL 3.5 and 4.0 for an NGINX fleet is a question of support windows and migration cost, not feature parity. OpenSSL 4.0 shipped in April 2026 but is explicitly not an LTS release. Under the project’s policy, non-LTS branches receive only 13 months of support. OpenSSL 3.5 is the current LTS, supported until April 2030. Moving an NGINX fleet from 3.5 to 4.0 today would cut the support window…
Read More... zstd-nginx-module: Maintained, Tested and Packaged
by Danila Vershinin, September 13, 2026
Technical Briefing: Maintained zstd Module for NGINX — Streaming Fixes, Packaging, and Audit Response Problem Statement The original tokers/zstd-nginx-module (by Alex Zhang) has not seen a release since 2023 and carries bugs in its streaming path that silently truncate large responses. Over the buffer size, the filter could close the zstd frame over unconsumed input, delivering a valid but short file with no error and no log line — a failure mode that passes header assertions and is invisible w…
Read More... NGINX RADIUS Authentication: No More htpasswd Files
by Danila Vershinin, September 12, 2026
Technical Briefing: RADIUS Authentication for NGINX Problem Statement NGINX ships with no built-in RADIUS support. Organizations that centralize credentials in FreeRADIUS, Microsoft NPS, Cisco ISE, or Aruba ClearPass have had no way to make NGINX defer to that authority—leaving per-tool htpasswd files as the practical alternative. The nginx-module-auth-radius package from the GetPageSpeed repository closes this gap by adding per-request RADIUS authentication (RFC 2865) to NGINX. How It Works Th…
Read More... ECH Without Padding Is a Lookup Table
by Danila Vershinin, September 11, 2026
Technical Briefing: Closing the ECH Handshake-Size Side Channel in NGINX Problem Statement Encrypted Client Hello (ECH) encrypts the inner ClientHello—including the real SNI—and pads it. But the server’s encrypted handshake flight (EncryptedExtensions, Certificate, CertificateVerify, Finished) still exposes its TLS record lengths on the wire. TLS 1.3 encrypts record contents but not lengths, and the dominant record is the certificate chain, which differs per virtual host. This means an observer…
Read More... NGINX TLS Vulnerability Fixes: BREACH, SWEET32, ROBOT
by Danila Vershinin, September 9, 2026
Here is the technical briefing based on the provided source summary. — Technical Briefing: Eliminating Legacy TLS Vulnerabilities and Achieving Post-Quantum Readiness in NGINX Problem Statement Four legacy TLS vulnerabilities—BREACH, Lucky13, SWEET32, and ROBOT—continue to dominate security scan reports for NGINX deployments. While the fixes are typically simple, they are often misapplied or missed due to configuration drift. Additionally, achieving post-quantum readiness requires specific so…
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