Three GoAhead TLS bugs skip CRLs, depth limits, or weaken DH
Original title: Three TLS Bugs in GoAhead
Fixes are in GoAhead 6.1.1 for the OpenSSL-compatible and mbed TLS cases; a public PoC decrypts weak DHE sessions.
GoAhead, an embedded web server used in large numbers of IoT, firewall, OT, and military devices, has three TLS-integration bugs that depend on the library and device settings. OpenSSL-compatible builds from 3.4.5 through 6.1.0 can load a CRL without enforcing it, so revoked client certificates complete mTLS (GOAHEAD-SA-2026-0006, CVSS 9.1). Legacy LibreSSL builds can accept an over-depth client chain when VERIFY_PEER=1 and VERIFY_ISSUER=0 (GOAHEAD-SA-2026-0004, CVSS 7.4). mbed TLS builds from 4.0.2 through 6.1.0 pass a one-byte DH modulus, and a researcher’s PoC decrypted a TLS 1.2 DHE_RSA session (GOAHEAD-SA-2026-0005, CVSS 5.9).
Unconfirmed: No in-the-wild exploitation is reported; decrypting DHE traffic requires a client that accepts the broken parameters.
- OpenSSL-compatible and mbed TLS fixes are GoAhead 6.1.1 or later.
- The CRL bug was shown on GoAhead 6.1.0 with OpenSSL 3.6.2.
- The broken DH group leaves eight possible shared secrets, the author says.
- Tested OpenSSL clients rejected the tiny modulus; ECDHE and TLS 1.3 are unaffected.
- LibreSSL mitigation is VERIFY_ISSUER=1 or moving to OpenSSL or LibreSSL 4.x.
Impact: Revoked clients accepted, over-depth chains allowed, or DHE sessions decryptable
| Product | Affected | Fixed in |
|---|---|---|
| GoAhead OpenSSL-compatible backend | >= 3.4.5, <= 6.1.0 | 6.1.1 |
| GoAhead mbed TLS backend | >= 4.0.2, <= 6.1.0 | 6.1.1 |
| GoAhead LibreSSL legacy verifier | 3.2.x or 3.3.2–3.3.6, <= 6.1.0 | — |
- 1.Upgrade OpenSSL-compatible and mbed TLS GoAhead builds to 6.1.1 or later.
- 2.Disable TLS 1.2 finite-field DHE suites or use the OpenSSL backend.
- 3.Set VERIFY_ISSUER=1 with a trusted CA bundle on affected LibreSSL builds.
From the original article
6 min read at foxio.io
GoAhead is used in hundreds of millions of IoT, Firewall, OT, and Military devices including those from Palo Alto Networks, Comcast, D-Link, HP, Canon, Honeywell, GE, Oracle, Siemens, Rockwell, Digi, Lockheed Martin, Boeing, and more.
By owenshen24 · foxio.io
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