NULL pointer dereference in Emqx Nanomq
CVE-2025-68699
NanoMQ MQTT Broker (NanoMQ) is an all-around Edge Messaging Platform. In version 0.24.6, NanoMQ has a protocol parsing / forwarding inconsistency when handling shared subscriptions ($share/). A malformed SUBSCRIBE topic such as $share/ab (missing the second /) is not strictly validated during the subscription stage, so the invalid Topic Filter is stored into the subscription table. Later, when any PUBLISH matches this subscription, the broker send path (nmq_pipe_send_start_v4/v5) performs a second $share/ parsing using strchr() and increments the returned pointer without NULL checks. If the second strchr() returns NULL, sub_topic++ turns the pointer into an invalid address (e.g. 0x1). This invalid pointer is then passed into topic_filtern(), which triggers strlen() and crashes with SIGSEGV. The crash is stable and remotely triggerable. This issue has been patched in version 0.24.7.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.003 (18.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 18th percentile — 18.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000
Affected products
- Emqx Nanomq — versions 0.24.6
- Nanomq — versions = 0.24.6
Weakness classification (CWE)
References
- github.com/nanomq/nanomq/security/advisories/GHSA-qv5f-c6v2-2f8h (Exploit, Vendor Advisory)
- github.com/nanomq/nanomq/commit/89d68d678e7f841ae7baa45cba8d9bc7ddc9ef4b (Patch)
Frequently asked questions
- What is CVE-2025-68699?
- CVE-2025-68699 is a medium-severity vulnerability in Emqx Nanomq, classified under NULL Pointer Dereference. CVSS score: 6.5/10. Published 2026-02-04.
- How severe is CVE-2025-68699?
- Medium severity. CVSS v3 base score is 6.5 out of 10.