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NVD / CVE Program· CNA Linux

CVE-2025-39889: Bluetooth: l2cap: Check encryption key size on incoming connection

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.09% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 24b2cdfc16e9bd6ab3d03b8e01c590755bd3141f, 522e9ed157e3c21b4dd623c79967f72c21e45b78, 9e3114958d87ea88383cbbf38c89e04b8ea1bce5.
  • Severity is disputed: the assigning authority (CNA) scores it 8.1, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 24b2cdfc16e9bd6ab3d03b8e01c590755bd3141f, 522e9ed157e3c21b4dd623c79967f72c21e45b78, 9e3114958d87ea88383cbbf38c89e04b8ea1bce5 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: l2cap: Check encryption key size on incoming connection This is required for passing GAP/SEC/SEM/BI-04-C PTS test case: Security Mode 4 Level 4, Responder - Invalid Encryption Key Size - 128 bit This tests the security key with size from 1 to 15 bytes while the Security Mode 4 Level 4 requests 16 bytes key size. Currently PTS fails with the following logs: - expected:Connection Response: Code: [3 (0x03)] Code Identifier: (lt)WildCard: Exists(gt) Length: [8 (0x0008)] Destination CID: (lt)WildCard: Exists(gt) Source CID: [64 (0x0040)] Result: [3 (0x0003)] Connection refused - Security block Status: (lt)WildCard: Exists(gt), but received:Connection Response: Code: [3 (0x03)] Code Identifier: [1 (0x01)] Length: [8 (0x0008)] Destination CID: [64 (0x0040)] Source CID: [64 (0x0040)] Result: [0 (0x0000)] Connection Successful Status: [0 (0x0000)] No further information available And HCI logs: < HCI Command: Read Encrypti.. (0x05|0x0008) plen 2 Handle: 14 Address: 00:1B:DC:F2:24:10 (Vencer Co., Ltd.) > HCI Event: Command Complete (0x0e) plen 7 Read Encryption Key Size (0x05|0x0008) ncmd 1 Status: Success (0x00) Handle: 14 Address: 00:1B:DC:F2:24:10 (Vencer Co., Ltd.) Key size: 7 > ACL Data RX: Handle 14 flags 0x02 dlen 12 L2CAP: Connection Request (0x02) ident 1 len 4 PSM: 4097 (0x1001) Source CID: 64 < ACL Data TX: Handle 14 flags 0x00 dlen 16 L2CAP: Connection Response (0x03) ident 1 len 8 Destination CID: 64 Source CID: 64 Result: Connection successful (0x0000) Status: No further information available (0x0000)

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Sep 24, 2025
Updated
Sep 25, 2026
EPSS
0.0% · 0th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.0%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.5
CNA · Linux
8.1
2.6 point gap

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2025-39889

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

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This vulnerability is about certificate validation or weak cryptography. The free SSL checker tests your certificate, enabled TLS versions and weak ciphers.

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Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel5.11 and later · before 5.15.181
  • linux linux kernel5.16 and later · before 6.1.135
  • linux linux kernel6.2 and later · before 6.6.88
  • linux linux kernel6.7 and later · before 6.12.25
  • linux linux kernel6.13 and later · before 6.14.4
  • linux linux kernel6.15

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.11affected
    • 4f911a538e089cce808a15dc3277250f4f8daef9 and later · before ed503d340a501e414114ddc614a3aae4f6e9eae2affected · git
    • 288c06973daae4637f25a0d1bdaf65fdbf8455f9 and later · before 24b2cdfc16e9bd6ab3d03b8e01c590755bd3141faffected · git
    • 288c06973daae4637f25a0d1bdaf65fdbf8455f9 and later · before c6d527bbd3d3896375079f5dbc8b7f96734a3ba5affected · git
    • 288c06973daae4637f25a0d1bdaf65fdbf8455f9 and later · before 9e3114958d87ea88383cbbf38c89e04b8ea1bce5affected · git
    • 288c06973daae4637f25a0d1bdaf65fdbf8455f9 and later · before d49798ecd26e0ee7995a7fc1e90ca5cd9b4402d6affected · git
    • 288c06973daae4637f25a0d1bdaf65fdbf8455f9 and later · before d4ca2fd218caafbf50e3343ba1260c6a23b5676aaffected · git
    • 288c06973daae4637f25a0d1bdaf65fdbf8455f9 and later · before 522e9ed157e3c21b4dd623c79967f72c21e45b78affected · git
    • before 5.11not affected · semver
    • 5.15.181 and later · up to and including 5.15.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.135-16.1.135-1
Debian:13linuxbefore 6.12.25-16.12.25-1
Debian:14linuxbefore 6.16.3-16.16.3-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-39888Sep 23, 2025 · fuse: Block access to folio overlimit
    31Monitor
  • ← EarlierCVE-2024-58241Sep 24, 2025 · Bluetooth: hci_core: Disable works on hci_unregister_dev
    22Monitor
  • Later →CVE-2025-39890Sep 24, 2025 · wifi: ath12k: fix memory leak in ath12k_service_ready_ext_event
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux24b2cdfc16e9bd6ab3d03b8e01c590755bd3141fVendor (CNA)
Linux Linux522e9ed157e3c21b4dd623c79967f72c21e45b78Vendor (CNA)
Linux Linux9e3114958d87ea88383cbbf38c89e04b8ea1bce5Vendor (CNA)
Linux Linuxc6d527bbd3d3896375079f5dbc8b7f96734a3ba5Vendor (CNA)
Linux Linuxd49798ecd26e0ee7995a7fc1e90ca5cd9b4402d6Vendor (CNA)
Linux Linuxd4ca2fd218caafbf50e3343ba1260c6a23b5676aVendor (CNA)
Linux Linuxed503d340a501e414114ddc614a3aae4f6e9eae2Vendor (CNA)
debian:linux6.1.135-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-43134224 days apartBluetooth: L2CAP: Fix missing key size check for L2CAP_LE_CONN_REQ
    32Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-326 · Inadequate Encryption Strength

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records