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FoxIO discloses three TLS flaws in GoAhead web server
Part of the GoAhead story · since 26 Oct
- Mon 26 Oct, 00:00 UTC. foxio.io, first report. FoxIO details three TLS bugs in GoAhead web server.
- Tue 27 Oct, 17:30 UTC. The Hacker News, its first report on the story. GoAhead TLS flaws let revoked certificates bypass checks.
- Wed 28 Oct, 04:01 UTC. SANS ISC, its first report on the story. eMudhra certificate compromise triggers revocations and system updates.
- Wed 28 Oct, 14:00 UTC. SecurityWeek, its first report on the story. FoxIO finds three TLS flaws in widely used GoAhead server.
- Thu 29 Oct, 02:00 UTC. SecurityOnline, its first report on the story. FoxIO discloses three TLS flaws in GoAhead web server. This article, 5th of 5.
FoxIO has published full details and proof‑of‑concept code for three GoAhead TLS vulnerabilities affecting the embedded web server used in a wide range of devices, including routers, switches, printers and industrial controllers. The advisories describe three issues with GoAhead’s TLS backends that can allow revoked certificates, bypass a chain‑depth limit or enable decryption of certain TLS sessions.
The most severe flaw, rated CVSS 9.1, concerns the OpenSSL‑compatible backend where revocation checks are never enabled despite loading a CRL, allowing a previously trusted but revoked client certificate to complete the mTLS handshake without warning. FoxIO assigns this bug GOAHEAD-SA-2026-0006 and notes that GoAhead 6.1.1 fixes all three issues.
A second issue, CVSS 7.4, affects builds using the legacy LibreSSL verifier (versions 3.2.x, 3.3.2–3.3.6). When an overly long certificate chain triggers an issuer error rather than a depth error, the server tolerates the issuer error if issuer verification is disabled, effectively bypassing the chain‑depth restriction. This is identified as GOAHEAD-SA-2026-0004.
The third flaw, CVSS 5.9, targets the Mbed TLS backend: a buffer length typo reduces a 2048‑bit DH modulus to a single byte, producing only eight possible shared secrets and potentially allowing a passive observer to decrypt TLS 1.2 DHE_RSA sessions, provided the client accepts the broken parameters; this is GOAHEAD-SA-2026-0005. FoxIO notes that some OpenSSL clients reject the parameters, while certain embedded or custom clients may not.
Official remediation is to upgrade to GoAhead 6.1.1 or later, after which the CRL checking and corrected DH length are in place, with guidance for mitigations if upgrading is not possible. FoxIO reports no confirmed exploits in the wild and notes no CVE identifiers appear in the advisory.
How the story developed
5 articles from 5 outlets since 26 Oct. Still developing; the latest report was 1 hour ago. This was the 5th report, 3 days after the first.
- Mon 26 Oct, 00:00 UTC. foxio.io, first report. FoxIO details three TLS bugs in GoAhead web server.
- Tue 27 Oct, 17:30 UTC. The Hacker News, its first report on the story. GoAhead TLS flaws let revoked certificates bypass checks.
- Wed 28 Oct, 04:01 UTC. SANS ISC, its first report on the story. eMudhra certificate compromise triggers revocations and system updates.
- Wed 28 Oct, 14:00 UTC. SecurityWeek, its first report on the story. FoxIO finds three TLS flaws in widely used GoAhead server.
- Thu 29 Oct, 02:00 UTC. SecurityOnline, its first report on the story. FoxIO discloses three TLS flaws in GoAhead web server. This article, 5th of 5.
- CVE not in KEV
- No CVE
- Larger: an outlet’s first report
- Coverage over time
Show all 5 articles as a listHide the list
- Mon 26 OctDay 01
- FoxIO details three TLS bugs in GoAhead web server00:00 · foxio.io · First report
Quiet for 2 days
Tue 27 OctDay 11- GoAhead TLS flaws let revoked certificates bypass checks17:30 · The Hacker News
- Wed 28 OctDay 22
- FoxIO finds three TLS flaws in widely used GoAhead server14:00 · SecurityWeek
- Thu 29 OctDay 31
- FoxIO discloses three TLS flaws in GoAhead web server02:00 · SecurityOnline · This article, 5th of 5