GoAhead vulnerability · the number 4 strikes again
Source Reddit Cybersecurity
Mentioned vulnerabilities
Rated by Threat Radar
Data as of 3 Nov 2026, 11:58 UTC
What to do
AI-suggested
EmbedThis released GoAhead version 6.1.1 on August 2, 2026, which fixes all described TLS vulnerabilities. Device makers should update their firmware to incorporate GoAhead 6.1.1. There are no interim mitigations for the OpenSSL revocation flaw. For LibreSSL builds, enabling issuer checking with a trusted CA bundle or upgrading to LibreSSL 4.x or OpenSSL is advised. For Mbed TLS, disabling finite-field DHE suites or using the OpenSSL backend mitigates the weak key exchange issue. After upgrading, EmbedThis recommends ending active sessions, restarting the server, and changing passwords stored with the Blowfish format. Users should monitor for firmware updates from device manufacturers, as the fix requires firmware replacement.
Discussion
Multiple TLS vulnerabilities were discovered in the GoAhead embedded web server, notably a critical flaw where revoked client certificates are accepted due to revocation checking being disabled despite loading a revocation list. This affects builds using the OpenSSL backend with mutual TLS enabled. Additional issues include a certificate chain length bypass in LibreSSL builds and a weak Diffie-Hellman key exchange in Mbed TLS builds. GoAhead 6.1.1, released August 2, 2026, fixes these issues. The vulnerabilities impact device makers who embed GoAhead in firmware for routers, printers, and industrial controllers. No known exploitation has been reported as of October 27, 2026.
r/cybersecurity (opens in a new tab)u/Cormacolinde0 points0 comments
I just read about this one.
CVE-2026-115881 and CVE-2026-115884: including issues with lack of revocation checking, mTLS validation bypass and a trivial DHE private value usage (this last one doesn’t have a CVE for some reason).
https://thehackernews.com/2026/10/goahead-tls-flaws-allow-revoked-client.html
The mTLS one seems most serious as that can allow improper authentication.
The DHE vulnerability is kind of hilarious, because it uses a single byte for one of its values, making one of the likely scenario of it using… “4”.
I found a few articles that mention Palo Alto using the library, but I can find no PA advisory yet. Anyone has info on that?