CVE-2026-110314
WebSocket frames keep reaching the WebSock after a server-initiated close in Bandit
Client-Side Enforcement of Server-Side Security vulnerability in the WebSocket connection handling of mtrudel bandit allows a remote client to keep running WebSock handler code after the server has stopped its connection, via data frames sent after ignoring the server's Close frame. When a WebSock callback returns {:stop, ...}, Bandit.WebSocket.Connection calls terminate/2, sends Close and shuts down the write side, but keeps the connection process running in a :closing state. handle_frame/3 and handle_info/3 never check that state, so later frames still reach handle_in/2 and later messages reach handle_info/2, with the state from the stop tuple, until the client sends Close, TCP drops or the idle timeout fires. A client refused in init/1 after a failed token check could still run an admin-only action. This issue affects bandit: from 0.5.1 before 1.14.0.
Fixes and workarounds
Workaround
Mark the WebSock state as stopped whenever a callback returns {:stop, ...}, and have handle_in/2 and handle_info/2 return {:ok, state} without acting while that mark is set.
Source: CNA: EEFFix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: EEFAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| bandit mtrudel bandit
hex |
≥ 0.5.1; < 1.14.0 (affected, semver)
Other versions: unaffected |
CNA: EEF |
| bandit mtrudel mtrudel/bandit
github |
≥ bb407f2277dcb65a58dd8cc07913a0b58a80e266; < 220b9dfd27f9a21305be2afc75cbe585ddc24e7a (affected, git)
Other versions: unaffected |
CNA: EEF |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 6.3 medium |
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N | CNA: EEF |
Exploit evidence
- https://github.com/mtrudel/bandit/security/advisories/GHSA-2v5v-8f9v-xh85
exploit · ADP: CISA-ADP
References
- https://github.com/mtrudel/bandit/security/advisories/GHSA-2v5v-8f9v-xh85CNA: EEF · vendor-advisory, related
- https://cna.erlef.org/cves/CVE-2026-110314.htmlCNA: EEF · related
- https://osv.dev/vulnerability/EEF-CVE-2026-110314CNA: EEF · related
- https://github.com/mtrudel/bandit/commit/bb407f2277dcb65a58dd8cc07913a0b58a80e266CNA: EEF · related
- https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7aCNA: EEF · patch
- https://github.com/mtrudel/bandit/security/advisories/GHSA-2v5v-8f9v-xh85ADP: CISA-ADP · exploit
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