# CVE-2026-10099: XX-Net V5.16.6 WebSocket Frame Parsing Data Corruption via simple_http_server.py

Status: published. Published: 2026-05-29. Updated: 2026-11-08.

XX-Net V5.16.6 contains a WebSocket frame parsing vulnerability in the WebSocket_receive_worker routine of simple_http_server.py that allows attackers to cause corrupted application data by sending unmasked WebSocket frames. The server unconditionally reads 4 bytes as a masking key regardless of whether the MASK bit is set in the frame header, causing the first 4 bytes of payload to be consumed as a mask key and the remaining payload to be incorrectly XOR-decoded, resulting in data corruption alongside missing RSV bit, opcode, and FIN fragmentation validations.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/XX-net/XX-Net/pull/14170
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/XX-net/XX-Net/commit/a68b972a84ed6e52df9f30237cf47493b9231b53

## Affected products and versions

- XX-net / XX-Net: ≥ 0; ≤ 5.16.6 (affected, git); ≥ 0; ≤ 43aec6f (affected, git). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 3.1: 4 (medium); CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N; source: CNA: VulnCheck

- CVSS 4.0: 5.1 (medium); CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: 0.13% as of 2026-11-08; percentile 2.21%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-1286

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/XX-net/XX-Net/issues/14169 (CNA: VulnCheck; issue-tracking)

- https://github.com/XX-net/XX-Net/pull/14170 (CNA: VulnCheck; issue-tracking, patch)

- https://github.com/XX-net/XX-Net/commit/a68b972a84ed6e52df9f30237cf47493b9231b53 (CNA: VulnCheck; patch)

- https://www.vulncheck.com/advisories/xx-net-websocket-frame-parsing-data-corruption-via-simple-http-server-py (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-10099; retrieved 2026-11-08; source updated 2026-11-08

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-10099; retrieved 2026-11-08; source updated Not reported

Revision: 33ff2b9d0bdc3d1200e991ff28f219b9491fba79ae497d85d8832d5cffee24b9

Canonical: https://y2.dev/cve/CVE-2026-10099

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