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CVE Record

CVE-2023-52885: SUNRPC: Fix UAF in svc_tcp_listen_data_ready()

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: Fix UAF in svc_tcp_listen_data_ready() After the listener svc_sock is freed, and before invoking svc_tcp_accept() for the established child sock, there is a window that the newsock retaining a freed listener svc_sock in sk_user_data which cloning from parent. In the race window, if data is received on the newsock, we will observe use-after-free report in svc_tcp_listen_data_ready(). Reproduce by two tasks: 1. while :; do rpc.nfsd 0 ; rpc.nfsd; done 2. while :; do echo "" | ncat -4 127.0.0.1 2049 ; done KASAN report: ================================================================== BUG: KASAN: slab-use-after-free in svc_tcp_listen_data_ready+0x1cf/0x1f0 [sunrpc] Read of size 8 at addr ffff888139d96228 by task nc/102553 CPU: 7 PID: 102553 Comm: nc Not tainted 6.3.0+ #18 Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020 Call Trace: <IRQ> dump_stack_lvl+0x33/0x50 print_address_description.constprop.0+0x27/0x310 print_report+0x3e/0x70 kasan_report+0xae/0xe0 svc_tcp_listen_data_ready+0x1cf/0x1f0 [sunrpc] tcp_data_queue+0x9f4/0x20e0 tcp_rcv_established+0x666/0x1f60 tcp_v4_do_rcv+0x51c/0x850 tcp_v4_rcv+0x23fc/0x2e80 ip_protocol_deliver_rcu+0x62/0x300 ip_local_deliver_finish+0x267/0x350 ip_local_deliver+0x18b/0x2d0 ip_rcv+0x2fb/0x370 __netif_receive_skb_one_core+0x166/0x1b0 process_backlog+0x24c/0x5e0 __napi_poll+0xa2/0x500 net_rx_action+0x854/0xc90 __do_softirq+0x1bb/0x5de do_softirq+0xcb/0x100 </IRQ> <TASK> ... </TASK> Allocated by task 102371: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 __kasan_kmalloc+0x7b/0x90 svc_setup_socket+0x52/0x4f0 [sunrpc] svc_addsock+0x20d/0x400 [sunrpc] __write_ports_addfd+0x209/0x390 [nfsd] write_ports+0x239/0x2c0 [nfsd] nfsctl_transaction_write+0xac/0x110 [nfsd] vfs_write+0x1c3/0xae0 ksys_write+0xed/0x1c0 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc Freed by task 102551: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 kasan_save_free_info+0x2a/0x50 __kasan_slab_free+0x106/0x190 __kmem_cache_free+0x133/0x270 svc_xprt_free+0x1e2/0x350 [sunrpc] svc_xprt_destroy_all+0x25a/0x440 [sunrpc] nfsd_put+0x125/0x240 [nfsd] nfsd_svc+0x2cb/0x3c0 [nfsd] write_threads+0x1ac/0x2a0 [nfsd] nfsctl_transaction_write+0xac/0x110 [nfsd] vfs_write+0x1c3/0xae0 ksys_write+0xed/0x1c0 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc Fix the UAF by simply doing nothing in svc_tcp_listen_data_ready() if state != TCP_LISTEN, that will avoid dereferencing svsk for all child socket.

HighCVSS 8.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2023-52885 is a Linux kernel memory safety bug in SUNRPC, used by NFS services. Under a timing race, network activity can cause the kernel to reference freed memory. The CVSS score is high, but exploitation complexity is high. No provided source or KEV listing indicates active exploitation.

Executive priority

Treat as high priority for Linux servers running NFS or exposed RPC services. The bug is serious but not currently known to be exploited from the provided sources. Patch through normal emergency or accelerated kernel maintenance, prioritizing exposed and business-critical file service infrastructure.

Technical view

The flaw is a use-after-free in svc_tcp_listen_data_ready(). A child TCP socket can retain stale sk_user_data copied from a freed listener svc_sock. If data arrives during that race window, SUNRPC may dereference freed memory. The kernel fix avoids dereferencing svsk when the socket state is not TCP_LISTEN.

Likely exposure

Linux systems using SUNRPC/NFS server functionality are the most relevant exposure. The CVE record lists Linux kernel versions including 4.8, 4.14.322, 4.19.291, 5.4.251, 5.10.188, 5.15.121, 6.1.39, 6.4.4, and 6.5 as affected.

Exploitation context

The CVSS vector is network, unauthenticated, no user interaction, but high attack complexity. The source describes a race involving NFS daemon lifecycle changes and incoming TCP traffic. There is no cited evidence of public exploitation or CISA KEV inclusion.

Researcher notes

Evidence comes from the Linux kernel CVE record and stable commits. The issue is a race-triggered UAF in SUNRPC TCP listener handling. The source includes KASAN evidence and a fix strategy, but exploitability beyond the described race is not established in the provided materials.

Mitigation direction

  • Apply Linux kernel or distribution updates that include the referenced stable fixes.
  • Prioritize systems exposing NFS/RPC services to untrusted networks.
  • Disable unnecessary NFS server or SUNRPC listener functionality where operationally feasible.
  • If patching is delayed, restrict network access to NFS/RPC services.
  • Track distribution advisories for backported fixes and supported kernel packages.

Validation and detection

  • Inventory Linux kernel versions across servers and appliances.
  • Identify hosts running NFS server or SUNRPC-related services.
  • Map installed kernels to vendor advisories or referenced stable commits.
  • Confirm updated kernels are booted, not merely installed.
  • Review network exposure for NFS/RPC services, especially internet-facing access.
Prepared
Confidence
high
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2023-52885 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.1 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
2ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.1CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H2.25.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

8.1High
CVSS 3.1 vector shape for CVE-2023-52885Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxfa9251afc33c81606d70cfe91800a779096442ec, fa9251afc33c81606d70cfe91800a779096442ec, fa9251afc33c81606d70cfe91800a779096442ec, fa9251afc33c81606d70cfe91800a779096442ec, fa9251afc33c81606d70cfe91800a779096442ec, fa9251afc33c81606d70cfe91800a779096442ec, fa9251afc33c81606d70cfe91800a779096442ec, fa9251afc33c81606d70cfe91800a779096442ecunaffected
LinuxLinux4.8, 0, 4.14.322, 4.19.291, 5.4.251, 5.10.188, 5.15.121, 6.1.39, 6.4.4, 6.5affected
Weakness

CWE details

No CWE listed

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