GoAhead TLS Flaw Lets Revoked Client Certificates Authenticate
Summary
CVE-2026-115881 lets revoked client certificates authenticate in affected GoAhead versions with a specific OpenSSL-compatible mutual TLS and CRL configuration. GoAhead 6.1.1 fixes the flaw; no in-the-wild exploitation is reported.
Key points
- The flaw affects GoAhead 3.4.5–6.1.0 when using the OpenSSL-compatible TLS backend with mutual TLS and a configured CRL.
- GoAhead loads the CRL but does not enable OpenSSL’s X509_V_FLAG_CRL_CHECK, so a revoked certificate may still authenticate.
- FoxIO reproduced the issue using GoAhead 6.1.0 and OpenSSL 3.6.2; the server gave no startup warning that revocation checking was ineffective.
- An attacker would need a certificate issued by a trusted authority that was later revoked, plus its associated private key; this is not a generic authentication bypass.
- GoAhead 6.1.1 fixes the issue. Embedded-device owners may need a firmware update from the device manufacturer.
- The article reports no known in-the-wild exploitation as of October 28, 2026. JA4Scan fingerprints can aid discovery but do not prove a device is vulnerable.
Article Details
- Vulnerability Types
- Improper certificate revocation validation in mutual TLS
- Severity
- Critical (CVSS 9.1)
- Affected Versions
- GoAhead 3.4.5 through 6.1.0, when using the OpenSSL-compatible TLS backend with a CRL configured
- Exploitation Status
- not_reported
- Exploit Availability
- public_poc
- Patch Status
- available
- Workarounds
- Restrict management interfaces to trusted networks, a VPN, or a dedicated administrative segment.
- Verify revocation enforcement using a dedicated test certificate.
- Review and revoke or replace affected credentials.
CVE
CVE-2026-115881Tracked as CVE-2026-115881, the flaw carries a vendor-assigned CVSS score of 9.1 and affects GoAhead versions 3.4.5 through 6.1.0 when the software uses its OpenSSL-compatible TLS backend with certificate revocationCVE-2026-115884A separate issue tracked as CVE-2026-115884 affects older LibreSSL verifier behavior and can allow an over-depth certificate chain to bypass GoAhead’s chain-depth restriction under a specific configuration where client
Vendors
Products
GoAheadA critical vulnerability in the GoAhead embedded web server can allow revoked client certificates to remain valid during mutual TLS authentication, potentially giving previously trusted identities continued access toLibreSSLA separate issue tracked as CVE-2026-115884 affects older LibreSSL verifier behavior and can allow an over-depth certificate chain to bypass GoAhead’s chain-depth restriction under a specific configuration where clientMbed TLSAnother flaw affects GoAhead builds using Mbed TLS.OpenSSLCVSS score of 9.1 and affects GoAhead versions 3.4.5 through 6.1.0 when the software uses its OpenSSL-compatible TLS backend with certificate revocation lists configured.
Tools
Industries
industrial systemsGoAhead is an embedded web server commonly integrated into routers, printers, gateways, industrial systems, and other network-connected products.IoTOrganizations operating IoT, OT, network infrastructure, or embedded devices should therefore track vendor advisories rather than relying solely on the upstream GoAhead release.OTOrganizations operating IoT, OT, network infrastructure, or embedded devices should therefore track vendor advisories rather than relying solely on the upstream GoAhead release.