Three TLS Flaws in GoAhead Web Server Put Some Device Configurations at Risk
Summary
FoxIO disclosed three TLS flaws in GoAhead that can undermine certificate revocation, expose some TLS 1.2 sessions to offline decryption, or bypass certificate-chain length limits. Risk depends on the TLS library and configuration.
Key points
- CVE-2026-115881 affects specified GoAhead versions using OpenSSL-compatible libraries with mTLS and CRLs: revoked client certificates may still be accepted because the server does not enable revocation checks.
- A flaw in GoAhead builds using Mbed TLS can weaken some TLS 1.2 connections, allowing recorded sessions to be decrypted offline if the client accepts the flawed parameters.
- CVE-2026-115884 can bypass client-certificate chain-length limits in specified LibreSSL builds when servers accept certificates from any issuer.
- FoxIO says each flaw affects only some deployments; exposure depends on the firmware's TLS library and certificate-check configuration.
- GoAhead 6.1.1 fixes the OpenSSL and Mbed TLS issues. FoxIO also recommends disabling finite-field DHE cipher suites or switching to OpenSSL for affected Mbed TLS builds.
- For the LibreSSL flaw, FoxIO recommends enabling issuer verification with a trusted CA bundle or switching to OpenSSL or LibreSSL 4.x.
- FoxIO released proof-of-concept code and fingerprints to help identify internet-facing GoAhead servers and their TLS libraries; it did not specify whether the named companies' products use vulnerable configurations.
Article Details
- Vulnerability Types
- TLS certificate revocation checks are not applied
- Weak encryption of some TLS 1.2 connections
- Client certificate chain-length limit bypass
- Severity
- Critical (CVSS 9.1); the other flaws have CVSS scores of 5.9 and 7.4
- Affected Versions
- GoAhead 3.4.5 through 6.1.0
- GoAhead 4.0.2 through 6.1.0
- GoAhead up to 6.1.0
- Exploitation Status
- unknown
- Exploit Availability
- public_poc
- Patch Status
- partial
- Workarounds
- For Mbed TLS builds, turn off finite-field DHE cipher suites or move to the OpenSSL backend.
- For the LibreSSL issue, enable issuer verification with a trusted CA bundle, or switch to OpenSSL or LibreSSL 4.x.
MITRE ATT&CK
CVE
CVE-2026-115881The critical flaw, CVE-2026-115881 (CVSS score of 9.1), impacts GoAhead 3.4.5 through 6.1.0 when built with OpenSSL or a compatible library and configured for mutual TLS (mTLS) with a certificate revocation list (CRL).CVE-2026-115884The chain-length bypass, CVE-2026-115884 (CVSS score of 7.4), affects GoAhead up to version 6.1.0 built with LibreSSL 3.2.x or 3.3.2 through 3.3.6.
People
Vendors
Products
GoAheadCybersecurity firm FoxIO has disclosed three vulnerabilities in GoAhead’s handling of TLS.LibreSSLThe chain-length bypass, CVE-2026-115884 (CVSS score of 7.4), affects GoAhead up to version 6.1.0 built with LibreSSL 3.2.x or 3.3.2 through 3.3.6.Mbed TLSfrom the second bug (CVSS score of 5.9, no CVE), found in GoAhead 4.0.2 through 6.1.0 builds that use Mbed TLS. A coding error weakens the encryption of some TLS 1.2 connections enough that recorded sessions can beOpenSSLThe critical flaw, CVE-2026-115881 (CVSS score of 9.1), impacts GoAhead 3.4.5 through 6.1.0 when built with OpenSSL or a compatible library and configured for mutual TLS (mTLS) with a certificate revocation list (CRL).
Industries
IoTAccording to FoxIO, it is present on hundreds of millions of devices across the IoT, OT, firewall and military sectors.MilitaryAccording to FoxIO, it is present on hundreds of millions of devices across the IoT, OT, firewall and military sectors.OTAccording to FoxIO, it is present on hundreds of millions of devices across the IoT, OT, firewall and military sectors.