Upstream information
Description
In Bouncy Castle for Java before 1.86, the Messaging Layer Security (MLS, RFC 9420) implementation did not bind an X.509 credential to a LeafNode's signature_key. LeafNode.verify() checked a leaf's signature against the signature_key carried in the leaf itself, while the credential's X.509 certificate chain was stored but never parsed or validated, so the end-entity certificate's public key was never required to match signature_key as RFC 9420 sec. 5.3 requires. A party could therefore present another party's certificate as its credential while signing the leaf, and the enclosing KeyPackage, with an unrelated key, and be accepted under that other party's identity through KeyPackage.verify() and the Group leaf-validation path. In a deployment that admits external commits without an independent credential-admission check, an unauthenticated attacker could be admitted under a victim's X.509 identity, evict the victim (resynchronization compares whole credentials rather than signing keys), derive the current epoch, decrypt subsequent group messages, and send messages accepted as the victim. TreeKEM.LeafNode now requires the end-entity certificate's subject public key, in the cipher suite's signature encoding, to equal signature_key for an X.509 credential and rejects the leaf otherwise, including an empty chain or a certificate whose key type does not match the cipher suite; certificate-chain and identity validation to a trust anchor remain the application's responsibility per RFC 9420 sec. 5.3.1. Deployments using only basic credentials are unaffected.Other Security Trackers
SUSE information
Overall state of this security issue: Pending
This issue is currently rated as having important severity.
| CVSS detail | SUSE |
|---|---|
| Base Score | 7.7 |
| Vector | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L |
| Attack Vector | Network |
| Attack Complexity | High |
| Privileges Required | None |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality Impact | High |
| Integrity Impact | High |
| Availability Impact | Low |
| CVSSv3 Version | 3.1 |
| CVSS detail | CNA (91579145-5d7b-4cc5-b925-a0262ff19630) | SUSE |
|---|---|---|
| Base Score | 9.2 | 9.2 |
| Vector | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N |
| Attack Vector | Network | Network |
| Attack Complexity | Low | Low |
| Attack Requirements | Present | Present |
| Privileges Required | None | None |
| User Interaction | None | None |
| Vulnerable System Confidentiality Impact | High | High |
| Vulnerable System Integrity Impact | High | High |
| Vulnerable System Availability Impact | Low | Low |
| Subsequent System Confidentiality Impact | None | None |
| Subsequent System Integrity Impact | None | None |
| Subsequent System Availability Impact | None | None |
| CVSSv4 Version | 4.0 | 4.0 |
Status of this issue by product and package
Please note that this evaluation state might be work in progress, incomplete or outdated. Also information for service packs in the LTSS phase is only included for issues meeting the LTSS criteria. If in doubt, feel free to contact us for clarification. The updates are grouped by state of their lifecycle. SUSE product lifecycles are documented on the lifecycle page.
| Product(s) | Source package | State |
|---|---|---|
| Products under general support and receiving all security fixes. | ||
| SUSE Linux Enterprise Desktop 15 SP7 | bouncycastle | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP7 | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP7 | bouncycastle | Affected |
| SUSE Linux Enterprise Server 16.0 | bouncycastle | Affected |
| SUSE Linux Enterprise Server 16.1 | bouncycastle | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | bouncycastle | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.0 | bouncycastle | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.1 | bouncycastle | Affected |
| openSUSE Leap 16.0 | bouncycastle | Affected |
| Products under Long Term Service Pack support and receiving important and critical security fixes. | ||
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5 | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | bouncycastle | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP4 | bouncycastle | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP5 | bouncycastle | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP6 | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP4 | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP5 | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP6 | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | bouncycastle | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | bouncycastle | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | bouncycastle | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | bouncycastle | Affected |
| Products past their end of life and not receiving proactive updates anymore. | ||
| SUSE Enterprise Storage 7 | bouncycastle | Affected |
| SUSE Enterprise Storage 7.1 | bouncycastle | Affected |
| SUSE Linux Enterprise Desktop 15 SP2 | bouncycastle | Affected |
| SUSE Linux Enterprise Desktop 15 SP3 | bouncycastle | Affected |
| SUSE Linux Enterprise Desktop 15 SP4 | bouncycastle | Affected |
| SUSE Linux Enterprise Desktop 15 SP5 | bouncycastle | Affected |
| SUSE Linux Enterprise Desktop 15 SP6 | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2 | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-ESPOS | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-LTSS | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3 | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-ESPOS | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4 | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | bouncycastle | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | bouncycastle | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP2 | bouncycastle | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP3 | bouncycastle | Affected |
| SUSE Linux Enterprise Real Time 15 SP2 | bouncycastle | Affected |
| SUSE Linux Enterprise Real Time 15 SP3 | bouncycastle | Affected |
| SUSE Linux Enterprise Real Time 15 SP4 | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP2 | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP2-BCL | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP2-LTSS | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP3 | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP3-BCL | bouncycastle | Affected |
| SUSE Linux Enterprise Server 15 SP3-LTSS | bouncycastle | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP2 | bouncycastle | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP3 | bouncycastle | Affected |
| SUSE Manager Proxy 4.1 | bouncycastle | Affected |
| SUSE Manager Proxy 4.2 | bouncycastle | Affected |
| SUSE Manager Proxy 4.3 | bouncycastle | Affected |
| SUSE Manager Retail Branch Server 4.1 | bouncycastle | Affected |
| SUSE Manager Retail Branch Server 4.2 | bouncycastle | Affected |
| SUSE Manager Retail Branch Server 4.3 | bouncycastle | Affected |
| SUSE Manager Server 4.1 | bouncycastle | Affected |
| SUSE Manager Server 4.2 | bouncycastle | Affected |
| SUSE Manager Server 4.3 | bouncycastle | Affected |
| openSUSE Leap 15.3 | bouncycastle | Affected |
| openSUSE Leap 15.4 | bouncycastle | Affected |
| openSUSE Leap 15.5 | bouncycastle | Affected |
| openSUSE Leap 15.6 | bouncycastle | Affected |
| Products at an unknown state of their lifecycle. | ||
| SUSE Linux Enterprise Server for NVIDIA 16.1 | bouncycastle | Affected |
| Container Status | ||
| containers/apache-pulsar:3.3 | bouncycastle | Affected |
SUSE Timeline for this CVE
CVE page created: Mon Oct 5 13:57:35 2026CVE page last modified: Tue Oct 6 19:43:23 2026