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GHSA-g3qj-j598-cxmq
No affected components available
Summary
fido2-lib v3.x depends on cbor-x (~1.6.0), which optionally pulls in cbor-extract (C++ native addon). cbor-extract <= 2.2.0 has a heap buffer over-read in extractStrings() — a 5-byte CBOR payload crashes Node.js with SIGSEGV. No JS exception, no try/catch, process dead.
The crash triggers during WebAuthn registration when the server decodes the attestation object. An attacker sends a crafted authenticator response to the registration endpoint — single request, unauthenticated, instant kill.
Fixed in cbor-extract@2.2.1 / cbor-x@1.6.3 (2026-03-08). fido2-lib@3.5.7 still pins cbor-x ~1.6.0 which resolves to vulnerable cbor-extract.
Affected versions
fido2-lib <= 3.5.7 (introduced cbor-x dependency). fido2-lib 2.x uses the old cbor package — not affected.
Only affects systems where cbor-extract native addon is installed (prebuilt binary available for platform). Pure JS fallback is safe.
PoC
const { decode } = require("cbor-x");
decode(Buffer.from("7a10000000", "hex")); // exit code 139 (SIGSEGV)
CBOR text string header claiming 268MB in a 5-byte buffer. extractStrings() in extract.cpp line 87 calls readString() without bounds check. Reads past buffer into unmapped memory.
In context: attacker intercepts WebAuthn registration response, replaces attestationObject with the 5-byte payload, POSTs to the registration verification endpoint. Server calls attestationResult() → cbor-x.decode() → cbor-extract → SIGSEGV.
Fix
Bump cbor-x to >= 1.6.3 (which pulls cbor-extract >= 2.2.1).
-"cbor-x": "~1.6.0"
+"cbor-x": "^1.6.3"
— Malik X (@Xvush)
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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