CVE-2026-19740

MEDIUMPre-NVD 6.56.5
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 6.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1% (below the 1st percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Trending — 3 sources updated this week
6.5EG
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: 0.1%CVSS: 6.5Exploit: None knownExposed services: Not assessed

A fix is referenced (a reference tagged "Patch", often a source commit), but no release containing it is confirmed — find the release that contains it; until it is applied, mitigate (WAF / firewall / segmentation).

The Link Layer Control Procedure (LLCP) implementation of the Zephyr software Bluetooth LE Controller retains the receive node that carried an accepted LL_PHY_UPDATE_IND so that it can later be reused for the host notification when the update instant is reached (llcp_rx_node_retain() in subsys/bluetooth/controller/ll_sw/ull_llcp.c, and the node is deliberately not recycled while marked NODE_RX_TYPE_RETAIN). The invalid-PDU arms of llcp_lp_pu_rx() and llcp_rp_pu_rx() in subsys/bluetooth/controller/ll_sw/ull_llcp_phy.c completed the procedure via llcp_lr_complete() / llcp_rr_complete() without first releasing that retained node, so the procedure context — the only remaining reference to the node — was freed while the node was still held out of the receive pool.

A peer device on an established LE connection can drive this deterministically and without pairing or encryption. Against a peripheral it sends LL_PHY_REQ, receives LL_PHY_RSP, sends a valid LL_PHY_UPDATE_IND with an instant a few connection events in the future (so the node becomes retained), and then, before the instant is reached, sends any other LL Control PDU such as LL_LENGTH_REQ; ull_cp_rx() routes it to the active remote PHY Update procedure, which takes the invalid-PDU path. The mirror case applies to a locally initiated PHY Update followed by an LL_REJECT_IND.

In the default configuration (CONFIG_BT_ASSERT and CONFIG_BT_CTLR_ASSERT_DEBUG both default y) the violated invariant in llcp_lr_check_done() / llcp_rr_check_done() triggers a controller assertion, ending in k_oops() (or k_panic()) — a single crafted PDU sequence from radio range faults the device. With those assertions compiled out, each attempt silently leaks one receive PDU node and its memq link; because the controller receive pool is small (PDU_RX_CNT, driven by CONFIG_BT_CTLR_RX_BUFFERS, which defaults to 1) and each attempt costs the attacker only a reconnect, a few repetitions exhaust the pool and leave Bluetooth inoperable until reboot. On releases v3.4.0 through v3.7.x the assertion is never reached, whatever the configuration, so every attempt leaks silently.

The impact is limited to availability: the orphaned node leaves no dangling pointer that is later dereferenced and is never delivered to the host, so there is no memory corruption or information disclosure. The same pull request applies the identical release to the Connection Update and CIS-create procedures, whose invalid-PDU arms had the same omission.

CVSS v3
6.5
EG Score
6.5MEDIUMmedium confidence
EG Risk
29
EG Risk 29/100

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)
Severity65% × 45%
The EG Score, 6.5 of 10.
Exploitation0.1% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it and apply that within your standard update timelines; until then, restrict network exposure of the affected system or apply the vendor's mitigation.
EPSS PROB
0.1%
EPSS %ILE
below the 1st
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it and apply that within your standard update timelines; until then, restrict network exposure of the affected system or apply the vendor's mitigation.

Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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)14 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's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” 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 11, 2026

Last Modified

October 13, 2026

Advisory Details (2)

Auto-updated Oct 11, 2026
🔬 Proof of concept available. Fix referenced — no release confirmed yet. Sources: github_commit, github.
GitHub advisoryMentions a patch (unverified)🟡 PoC Available

Bluetooth LE Controller: retained RX node leak and reachable assertion in the PHY Update procedure · Advisory · zephyrproject-rtos/zephyr · GitHub

https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-rgw4-3qr8-pp36
GitHub commit

commit 06bf10e3de16 (zephyrproject-rtos/zephyr)

Fix landed in zephyrproject-rtos/zephyr commit 06bf10e3de16 — awaiting tagged release

https://github.com/zephyrproject-rtos/zephyr/commit/06bf10e3de16b57b864f969330188b59f7d69a63

Weakness Classification(4)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 8× 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.

  1. 2026-10-13 17:07 UTCEG score recompute
  2. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.1% · below the 1st percentile
  3. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.1% · below the 1st percentile
  4. 2026-10-12 16:25 UTCEG score recompute
  5. 2026-10-11 20:06 UTCEG score recompute
  6. 2026-10-11 18:27 UTCEG score recompute
  7. 2026-10-11 17:27 UTCEG score recomputeFirst assessed: 6.5 MEDIUM
  8. 2026-10-11 17:25 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-19740?
CVE-2026-19740 is a medium-severity vulnerability; its CVE record was published on October 11, 2026. The Link Layer Control Procedure (LLCP) implementation of the Zephyr software Bluetooth LE Controller retains the receive node that carried an accepted LLPHYUPDATEIND so that it can later be reused for the host notification when the update instant is reached (llcprxnoderetain() in…
When was the CVE record for CVE-2026-19740 published?
The CVE record for CVE-2026-19740 was published on October 11, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. 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-2026-19740 actively exploited?
CVE-2026-19740 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.1% probability of exploitation in the next 30 days (below the 1st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-19740?
CVE-2026-19740 has a CVSS base score of 6.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-19740?
A fix for CVE-2026-19740 is referenced (a reference tagged "Patch", often a source commit), but EchelonGraph has no release containing it on record. Check that reference and the vendor's advisory for a release that contains the fix and update to it; until then, restrict network exposure of the affected system or apply the vendor's mitigation.

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