VULNERABILITY

Ubuntu: (Multiple Advisories) (CVE-2025-21796): Linux kernel vulnerabilities

Try Surface Command Get a continuous 360° view of your attack surface
Back to Search

Ubuntu: (Multiple Advisories) (CVE-2025-21796): Linux kernel vulnerabilities

Severity
7
CVSS
(AV:L/AC:L/Au:S/C:C/I:C/A:C)
Published
02/27/2025
Created
05/21/2025
Added
05/20/2025
Modified
05/22/2025

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: clear acl_access/acl_default after releasing them If getting acl_default fails, acl_access and acl_default will be released simultaneously. However, acl_access will still retain a pointer pointing to the released posix_acl, which will trigger a WARNING in nfs3svc_release_getacl like this: ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 26 PID: 3199 at lib/refcount.c:28 refcount_warn_saturate+0xb5/0x170 Modules linked in: CPU: 26 UID: 0 PID: 3199 Comm: nfsd Not tainted 6.12.0-rc6-00079-g04ae226af01f-dirty #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:refcount_warn_saturate+0xb5/0x170 Code: cc cc 0f b6 1d b3 20 a5 03 80 fb 01 0f 87 65 48 d8 00 83 e3 01 75 e4 48 c7 c7 c0 3b 9b 85 c6 05 97 20 a5 03 01 e8 fb 3e 30 ff <0f> 0b eb cd 0f b6 1d 8a3 RSP: 0018:ffffc90008637cd8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff83904fde RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffff88871ed36380 RBP: ffff888158beeb40 R08: 0000000000000001 R09: fffff520010c6f56 R10: ffffc90008637ab7 R11: 0000000000000001 R12: 0000000000000001 R13: ffff888140e77400 R14: ffff888140e77408 R15: ffffffff858b42c0 FS: 0000000000000000(0000) GS:ffff88871ed00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000562384d32158 CR3: 000000055cc6a000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ? refcount_warn_saturate+0xb5/0x170 ? __warn+0xa5/0x140 ? refcount_warn_saturate+0xb5/0x170 ? report_bug+0x1b1/0x1e0 ? handle_bug+0x53/0xa0 ? exc_invalid_op+0x17/0x40 ? asm_exc_invalid_op+0x1a/0x20 ? tick_nohz_tick_stopped+0x1e/0x40 ? refcount_warn_saturate+0xb5/0x170 ? refcount_warn_saturate+0xb5/0x170 nfs3svc_release_getacl+0xc9/0xe0 svc_process_common+0x5db/0xb60 ? __pfx_svc_process_common+0x10/0x10 ? __rcu_read_unlock+0x69/0xa0 ? __pfx_nfsd_dispatch+0x10/0x10 ? svc_xprt_received+0xa1/0x120 ? xdr_init_decode+0x11d/0x190 svc_process+0x2a7/0x330 svc_handle_xprt+0x69d/0x940 svc_recv+0x180/0x2d0 nfsd+0x168/0x200 ? __pfx_nfsd+0x10/0x10 kthread+0x1a2/0x1e0 ? kthread+0xf4/0x1e0 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x34/0x60 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> Kernel panic - not syncing: kernel: panic_on_warn set ... Clear acl_access/acl_default after posix_acl_release is called to prevent UAF from being triggered.

Solution(s)

  • ubuntu-upgrade-linux-image-5-15-0-1037-nvidia-tegra
  • ubuntu-upgrade-linux-image-5-15-0-1037-nvidia-tegra-rt
  • ubuntu-upgrade-linux-image-5-15-0-1066-gkeop
  • ubuntu-upgrade-linux-image-5-15-0-1076-ibm
  • ubuntu-upgrade-linux-image-5-15-0-1077-intel-iot-realtime
  • ubuntu-upgrade-linux-image-5-15-0-1078-nvidia
  • ubuntu-upgrade-linux-image-5-15-0-1078-nvidia-lowlatency
  • ubuntu-upgrade-linux-image-5-15-0-1079-intel-iotg
  • ubuntu-upgrade-linux-image-5-15-0-1080-kvm
  • ubuntu-upgrade-linux-image-5-15-0-1081-gke
  • ubuntu-upgrade-linux-image-5-15-0-1081-oracle
  • ubuntu-upgrade-linux-image-5-15-0-1083-gcp
  • ubuntu-upgrade-linux-image-5-15-0-1083-gcp-fips
  • ubuntu-upgrade-linux-image-5-15-0-1084-realtime
  • ubuntu-upgrade-linux-image-5-15-0-1089-azure
  • ubuntu-upgrade-linux-image-5-15-0-1089-azure-fips
  • ubuntu-upgrade-linux-image-5-15-0-140-fips
  • ubuntu-upgrade-linux-image-5-15-0-140-generic
  • ubuntu-upgrade-linux-image-5-15-0-140-generic-64k
  • ubuntu-upgrade-linux-image-5-15-0-140-generic-lpae
  • ubuntu-upgrade-linux-image-5-15-0-140-lowlatency
  • ubuntu-upgrade-linux-image-5-15-0-140-lowlatency-64k
  • ubuntu-upgrade-linux-image-6-11-0-1010-realtime
  • ubuntu-upgrade-linux-image-6-11-0-1013-raspi
  • ubuntu-upgrade-linux-image-6-11-0-1015-azure
  • ubuntu-upgrade-linux-image-6-11-0-1015-azure-fde
  • ubuntu-upgrade-linux-image-6-11-0-1015-gcp
  • ubuntu-upgrade-linux-image-6-11-0-1015-gcp-64k
  • ubuntu-upgrade-linux-image-6-11-0-1022-oem
  • ubuntu-upgrade-linux-image-6-11-0-26-generic
  • ubuntu-upgrade-linux-image-6-11-0-26-generic-64k
  • ubuntu-upgrade-linux-image-azure
  • ubuntu-upgrade-linux-image-azure-cvm
  • ubuntu-upgrade-linux-image-azure-fde
  • ubuntu-upgrade-linux-image-azure-fips
  • ubuntu-upgrade-linux-image-azure-lts-22-04
  • ubuntu-upgrade-linux-image-fips
  • ubuntu-upgrade-linux-image-gcp
  • ubuntu-upgrade-linux-image-gcp-64k
  • ubuntu-upgrade-linux-image-gcp-fips
  • ubuntu-upgrade-linux-image-gcp-lts-22-04
  • ubuntu-upgrade-linux-image-generic
  • ubuntu-upgrade-linux-image-generic-64k
  • ubuntu-upgrade-linux-image-generic-64k-hwe-24-04
  • ubuntu-upgrade-linux-image-generic-hwe-24-04
  • ubuntu-upgrade-linux-image-generic-lpae
  • ubuntu-upgrade-linux-image-gke
  • ubuntu-upgrade-linux-image-gke-5-15
  • ubuntu-upgrade-linux-image-gkeop
  • ubuntu-upgrade-linux-image-gkeop-5-15
  • ubuntu-upgrade-linux-image-ibm
  • ubuntu-upgrade-linux-image-intel-iot-realtime
  • ubuntu-upgrade-linux-image-intel-iotg
  • ubuntu-upgrade-linux-image-kvm
  • ubuntu-upgrade-linux-image-lowlatency
  • ubuntu-upgrade-linux-image-lowlatency-64k
  • ubuntu-upgrade-linux-image-lowlatency-64k-hwe-20-04
  • ubuntu-upgrade-linux-image-lowlatency-hwe-20-04
  • ubuntu-upgrade-linux-image-nvidia
  • ubuntu-upgrade-linux-image-nvidia-lowlatency
  • ubuntu-upgrade-linux-image-nvidia-tegra
  • ubuntu-upgrade-linux-image-nvidia-tegra-rt
  • ubuntu-upgrade-linux-image-oem-24-04b
  • ubuntu-upgrade-linux-image-oracle
  • ubuntu-upgrade-linux-image-oracle-lts-22-04
  • ubuntu-upgrade-linux-image-raspi
  • ubuntu-upgrade-linux-image-realtime
  • ubuntu-upgrade-linux-image-virtual
  • ubuntu-upgrade-linux-image-virtual-hwe-24-04

References

View more

insightVM

Advanced vulnerability management analytics and reporting.
Key Features
  • Lightweight Endpoint Agent
  • Live Dashboards
  • Real Risk Prioritization
  • IT-Integrated Remediation Projects
  • Cloud, Virtual, and Container Assessment
  • Integrated Threat Feeds
  • Easy-to-Use RESTful API
  • Automation-Assisted Patching
  • Automated Containment
Free InsightVM Trial View All Features

With Rapid7 live dashboards, I have a clear view of all the assets on my network, which ones can be exploited, and what I need to do in order to reduce the risk in my environment in real-time. No other tool gives us that kind of value and insight.

– Scott Cheney, Manager of Information Security, Sierra View Medical Center

;