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Google: sys-kernel/csql-kernel-6_1, sys-kernel/csql-kernel-6_6: security update to 18613.263.49

medium Tenable Self-Hosted Container Security Plugin ID 471312

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

 - In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Load DR6 with guest value
 only before entering .vcpu_run() loop Move the conditional loading of hardware DR6 with the guest's DR6
 value out of the core .vcpu_run() loop to fix a bug where KVM can load hardware with a stale
 vcpu->arch.dr6. When the guest accesses a DR and host userspace isn't debugging the guest, KVM disables DR
 interception and loads the guest's values into hardware on VM-Enter and saves them on VM-Exit. This allows
 the guest to access DRs at will, e.g. so that a sequence of DR accesses to configure a breakpoint only
 generates one VM-Exit. For DR0-DR3, the logic/behavior is identical between VMX and SVM, and also
 identical between KVM_DEBUGREG_BP_ENABLED (userspace debugging the guest) and KVM_DEBUGREG_WONT_EXIT
 (guest using DRs), and so KVM handles loading DR0-DR3 in common code, _outside_ of the core
 kvm_x86_ops.vcpu_run() loop. But for DR6, the guest's value doesn't need to be loaded into hardware for
 KVM_DEBUGREG_BP_ENABLED, and SVM provides a dedicated VMCB field whereas VMX requires software to manually
 load the guest value, and so loading the guest's value into DR6 is handled by {svm,vmx}_vcpu_run(), i.e.
 is done _inside_ the core run loop. Unfortunately, saving the guest values on VM-Exit is initiated by
 common x86, again outside of the core run loop. If the guest modifies DR6 (in hardware, when DR
 interception is disabled), and then the next VM-Exit is a fastpath VM-Exit, KVM will reload hardware DR6
 with vcpu->arch.dr6 and clobber the guest's actual value. The bug shows up primarily with nested VMX
 because KVM handles the VMX preemption timer in the fastpath, and the window between hardware DR6 being
 modified (in guest context) and DR6 being read by guest software is orders of magnitude larger in a nested
 setup. E.g. in non-nested, the VMX preemption timer would need to fire precisely between #DB injection and
 the #DB handler's read of DR6, whereas with a KVM-on-KVM setup, the window where hardware DR6 is "dirty"
 extends all the way from L1 writing DR6 to VMRESUME (in L1). L1's view: ========== <L1 disables DR
 interception> CPU 0/KVM-7289 [023] d.... 2925.640961: kvm_entry: vcpu 0 A: L1 Writes DR6 CPU 0/KVM-7289
 [023] d.... 2925.640963: <hack>: Set DRs, DR6 = 0xffff0ff1 B: CPU 0/KVM-7289 [023] d.... 2925.640967:
 kvm_exit: vcpu 0 reason EXTERNAL_INTERRUPT intr_info 0x800000ec D: L1 reads DR6, arch.dr6 = 0 CPU
 0/KVM-7289 [023] d.... 2925.640969: <hack>: Sync DRs, DR6 = 0xffff0ff0 CPU 0/KVM-7289 [023] d....
 2925.640976: kvm_entry: vcpu 0 L2 reads DR6, L1 disables DR interception CPU 0/KVM-7289 [023] d....
 2925.640980: kvm_exit: vcpu 0 reason DR_ACCESS info1 0x0000000000000216 CPU 0/KVM-7289 [023] d....
 2925.640983: kvm_entry: vcpu 0 CPU 0/KVM-7289 [023] d.... 2925.640983: <hack>: Set DRs, DR6 = 0xffff0ff0
 L2 detects failure CPU 0/KVM-7289 [023] d.... 2925.640987: kvm_exit: vcpu 0 reason HLT L1 reads DR6
 (confirms failure) CPU 0/KVM-7289 [023] d.... 2925.640990: <hack>: Sync DRs, DR6 = 0xffff0ff0 L0's view:
 ========== L2 reads DR6, arch.dr6 = 0 CPU 23/KVM-5046 [001] d.... 3410.005610: kvm_exit: vcpu 23 reason
 DR_ACCESS info1 0x0000000000000216 CPU 23/KVM-5046 [001] ..... 3410.005610: kvm_nested_vmexit: vcpu 23
 reason DR_ACCESS info1 0x0000000000000216 L2 => L1 nested VM-Exit CPU 23/KVM-5046 [001] ..... 3410.005610:
 kvm_nested_vmexit_inject: reason: DR_ACCESS ext_inf1: 0x0000000000000216 CPU 23/KVM-5046 [001] d....
 3410.005610: kvm_entry: vcpu 23 CPU 23/KVM-5046 [001] d.... 3410.005611: kvm_exit: vcpu 23 reason VMREAD
 CPU 23/KVM-5046 [001] d.... 3410.005611: kvm_entry: vcpu 23 CPU 23/KVM-5046 [001] d.... 3410.
 ---truncated--- (CVE-2025-21839)

Solution

Update the sys-kernel/csql-kernel-6_1 library and its related packages to version 18613.263.49 or later.

See Also

https://storage.googleapis.com/cos-oval-vulnerability-feed/cos-117.oval.xml.tar.gz

Plugin Details

Severity: Medium

ID: 471312

Version: Revision 1.2

Type: Local

Published: 10/3/2026

Updated: 10/3/2026

Supported Sensors: Tenable Cloud Security, Tenable Self-Hosted Container Security

Risk Information

VPR

Risk Factor: Medium

Score: 5

Percentile: 94.89

Vendor

Vendor Severity: MEDIUM

CVSS v2

Risk Factor: Medium

Base Score: 4.6

Temporal Score: 3.4

Vector: CVSS2#AV:L/AC:L/Au:S/C:N/I:N/A:C

CVSS Score Source: CVE-2025-21839

CVSS v3

Risk Factor: Medium

Base Score: 5.5

Temporal Score: 4.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 3/7/2025

Reference Information

CVE: CVE-2025-21839