RT-Thread through 5.3.0 contains a memory corruption vulnerability in the legacy USB CDC virtual COM port driver that aliases rx_ringbuffer as a Serial V2 rt_serial_rx_fifo in _function_enable(). A connected USB host configuring the CDC device triggers writes past the ring buffer into struct vcom members and an invalid rt_free() on close, causing denial of service.
CVE-2026-108952
MEDIUMPre-NVD 4.64.6Trending — 4 sources updated this week
EchelonGraph scoreHIGH confidence
“—” beside the score: it is equal to the CVSS score beside it.
Score 4.6 from GitHub Security Advisory published 2026-10-12. A secondary CVSS source baseline 4.6; sources differ by 0.0.
Triggered by: GitHub Security Advisory CVSS
Sources: GitHub Security Advisory, a secondary CVSS source
4.6EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 4.6Exploit: None knownExposed services: Not assessed
An upstream fix is merged but not yet released — mitigate (WAF / firewall / segmentation) until the release ships, then apply it.
- CVSS v3
- 4.6
- EG Score
- 4.6MEDIUMhigh confidence
- EG Risk
- 21EG Risk 21/100
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computed (value × EchelonGraph’s weight)Severity46% × 45%The EG Score, 4.6 of 10.Exploitation0% × 40%No KEV listing, EG-KEV tier or EPSS when EchelonGraph scored this CVE.Automatability0% × 15%CISA's SSVC Automatable value: no (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines until it ships, then apply the release. - EPSS PROB
- 0.2%
- EPSS %ILE
- 9th
- KEV
- Not listed
SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.
An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines until it ships, then apply the release.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
October 12, 2026
Last Modified
October 13, 2026
Advisory Details (6)
Auto-updated Oct 12, 2026Upstream fix merged — awaiting tagged release. Sources: github_pr, github_commit.
Web page
RT-Thread through 5.3.0 Memory Corruption via USB CDC VCOM Driver | Advisories | VulnCheck
https://www.vulncheck.com/advisories/rt-thread-through-5.3.0-memory-corruption-via-usb-cdc-vcom-driverWeb page
GitHub - RT-Thread/rt-thread: RT-Thread is an open source IoT Real-Time Operating System (RTOS). https://rt-thread.github.io/rt-thread/ · GitHub
https://github.com/RT-Thread/rt-threadWeb page
rt-thread/components/legacy/usb/usbdevice/class/cdc_vcom.c at 99428a1e7f7447955aa860f7c969273a12095b8f · RT-Thread/rt-thread · GitHub
https://github.com/RT-Thread/rt-thread/blob/99428a1e7f7447955aa860f7c969273a12095b8f/components/legacy/usb/usbdevice/class/cdc_vcom.c#L518GitHub commit
commit ceef6e0ccd64 (RT-Thread/rt-thread)
Fix landed in RT-Thread/rt-thread commit ceef6e0ccd64 — awaiting tagged release
https://github.com/RT-Thread/rt-thread/commit/ceef6e0ccd646aef61b907aeb9f29269d1caba50GitHub pull request
fix[usb]: stop aliasing rt_ringbuffer as rt_serial_rx_fifo in VCOM
Fix merged in RT-Thread/rt-thread PR #11770 on 2026-10-11 — awaiting tagged release
https://github.com/RT-Thread/rt-thread/pull/11770Web page
[Bug] Legacy USB CDC VCOM uses rt_ringbuffer as rt_serial_rx_fifo with Serial V2 · Issue #11739 · RT-Thread/rt-thread · GitHub
https://github.com/RT-Thread/rt-thread/issues/11739Vendor Advisories for CVE-2026-108952(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 9× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
- 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.2% · 9th percentile
- 2026-10-13 15:29 UTCEG score recompute
- 2026-10-13 15:29 UTCGHSA enrichmentGHSA-x4hq-c3c6-m368 · GitHub CVSS 4.6
- 2026-10-13 15:07 UTCEG score recompute
- 2026-10-13 15:07 UTCGHSA enrichmentGHSA-x4hq-c3c6-m368 · GitHub CVSS 4.6
- 2026-10-12 16:38 UTCEG score recompute
- 2026-10-12 13:26 UTCEG score recompute
- 2026-10-12 12:32 UTCEG score recomputeFirst assessed: 4.6 MEDIUM
- 2026-10-12 12:31 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-108952?
CVE-2026-108952 is a medium-severity vulnerability; its CVE record was published on October 12, 2026. RT-Thread through 5.3.0 contains a memory corruption vulnerability in the legacy USB CDC virtual COM port driver that aliases rxringbuffer as a Serial V2 rtserialrxfifo in functionenable(). A connected USB host configuring the CDC device triggers writes past the ring buffer into struct vcom members…
When was CVE-2026-108952 made public?
CVE-2026-108952 was made public on August 23, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on October 12, 2026. EchelonGraph's copy of the record carries a last-modified date of October 13, 2026; the record at its source may have been updated since.
Is CVE-2026-108952 actively exploited?
CVE-2026-108952 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (9th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-108952?
CVE-2026-108952 has a CVSS base score of 4.6 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-108952?
An upstream fix for CVE-2026-108952 has been merged but is not yet in a tagged release. Until it ships, restrict network exposure of the affected system or apply the vendor's mitigation, then update to the release that contains the fix. The vendor advisories EchelonGraph has for CVE-2026-108952 are linked in the Vendor Advisories panel on this page.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-108952
Is Your Infrastructure Affected by CVE-2026-108952?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.