Forge: TLS client crash on a handshake record received without a session
### Summary
A `forge.tls` client throws an uncaught `TypeError` from `connection.process()` when it receives a ServerHello while it has no session: after a `close_notify` alert or a call to `close()`, or before `handshake()` is called. A malicious server or an on-path attacker can use this to terminate a Node.js process. Fixed in node-forge 1.4.3.
### Details
`tls.handleHandshake()` in `lib/tls.js` updates the handshake digests with `c.session.md5.update(bytes)` before it calls the message handler. A client creates its session in `handshake()`, and `c.reset()` sets it to `null` when the connection is closed. Closing doesn't set the fail flag, and the client goes back to expecting a ServerHello, so a Handshake record received afterwards still reaches `handleHandshake()`, which throws `TypeError: Cannot read properties of null (reading 'md5')`.
This happens:
- after the server sends a `close_notify` alert (at any alert level);
- after the application calls `close()`;
- before the application calls `handshake()`.
The exception propagates out of `connection.process()`. Applications that pass socket data to `process()` from a `data` event handler without catching exceptions, as in the README example, terminate. After a reset the connection uses no encryption, so an on-path attacker can inject the records even when the real server is honest.
Servers are not affected: a server creates its session when it receives a ClientHello.
The fix handles these records like other unexpected records on a closed client: they are ignored.
#### Patches
Fixed in node-forge 1.4.3.
#### Workarounds
Catch exceptions thrown by `connection.process()` and close the socket, or stop passing socket data to `process()` once the `closed` callback has been called and until `handshake()` is called again.
#### Resources
- RFC 5246, section 7.2.1 (Closure Alerts): https://www.rfc-editor.org/rfc/rfc5246#section-7.2.1
- Related: GHSA-525v-9gp9-w22h (another TLS client `TypeError`, fixed in 1.4.1): https://github.com/digitalbazaar/forge/security/advisories/GHSA-525v-9gp9-w22h
#### Severity
CVSS 3.1: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H (5.9, Moderate)
CVSS 4.0 (informational): CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N (8.2)
CVSS 4.0 has no counterpart to 3.1's AC:H beyond AT:P and scores this higher; the severity rating follows CVSS 3.1.
#### Credits
Reported by @manus-use.
### Proof of concept
var c = forge.tls.createConnection({server: false, ...});
c.handshake();
// warning close_notify alert, then an empty ServerHello, in separate
// process() calls
c.process(forge.util.hexToBytes('15030100020100'));
c.process(forge.util.hexToBytes('160301000402000000'));
// <= 1.4.2: TypeError: Cannot read properties of null (reading 'md5')
// 1.4.3: the record is ignored
The reporter's PoC is in tests/pocs/ghsa-j8rw-jp99-435v.js, and regression tests are in tests/unit/tls.js.
### Impact
Applications that use `forge.tls` as a client and pass data from a network socket to `connection.process()` are affected. The server they connect to, or an on-path attacker, can make `process()` throw; if the application doesn't catch it, the Node.js process terminates, dropping all its connections. Servers built on `forge.tls` are not affected. There is no confidentiality or integrity impact.
- Source published
- 10 Nov 2026 21:14:26 UTC
- Source modified
- 10 Nov 2026 21:30:04 UTC
- Saved here
- 10 Nov 2026 22:21:40 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Publisher rating · MODERATE