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CVE Record

CVE-2023-53557: fprobe: Release rethook after the ftrace_ops is unregistered

In the Linux kernel, the following vulnerability has been resolved: fprobe: Release rethook after the ftrace_ops is unregistered While running bpf selftests it's possible to get following fault: general protection fault, probably for non-canonical address \ 0x6b6b6b6b6b6b6b6b: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC NOPTI ... Call Trace: <TASK> fprobe_handler+0xc1/0x270 ? __pfx_bpf_testmod_init+0x10/0x10 ? __pfx_bpf_testmod_init+0x10/0x10 ? bpf_fentry_test1+0x5/0x10 ? bpf_fentry_test1+0x5/0x10 ? bpf_testmod_init+0x22/0x80 ? do_one_initcall+0x63/0x2e0 ? rcu_is_watching+0xd/0x40 ? kmalloc_trace+0xaf/0xc0 ? do_init_module+0x60/0x250 ? __do_sys_finit_module+0xac/0x120 ? do_syscall_64+0x37/0x90 ? entry_SYSCALL_64_after_hwframe+0x72/0xdc </TASK> In unregister_fprobe function we can't release fp->rethook while it's possible there are some of its users still running on another cpu. Moving rethook_free call after fp->ops is unregistered with unregister_ftrace_function call.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux kernel fprobe cleanup race can leave another CPU using memory after it has been released. The observed result was a kernel protection fault. A local, low-privileged user may potentially compromise confidentiality, integrity, or availability, according to the supplied CVSS assessment, but the bundle does not demonstrate practical exploitation.

Executive priority

Treat as a high-priority kernel maintenance issue, especially on shared Linux systems or hosts running untrusted workloads. It requires local access rather than remote reachability, and active exploitation is not established. Schedule prompt vendor-approved updates while prioritizing externally managed, multi-tenant, and privileged infrastructure.

Technical view

During unregister_fprobe, fp->rethook could be freed while handlers on another CPU still referenced it. This lifecycle race produced a protection fault during BPF selftests. The kernel fix unregisters the associated ftrace function before freeing the rethook, preventing remaining users from accessing released memory.

Likely exposure

Exposure is limited to Linux systems running affected kernel revisions where fprobe functionality can be exercised. The supplied data identifies affected versions including 5.18, 6.1.40, 6.4.5, and 6.5, but its version ranges are incomplete or ambiguous. Confirm status against distribution kernel guidance and the referenced stable commits.

Exploitation context

The CVSS vector describes local access, low privileges, low complexity, and no user interaction. The failure was observed during BPF selftests. The bundle provides no evidence of public weaponization or real-world exploitation, and CVE-2023-53557 is not identified as a CISA KEV entry.

Researcher notes

The evidence supports a cross-CPU lifetime race involving rethook cleanup after fprobe unregistration. The poisoned 0x6b pattern is consistent with access to released memory, but no CWE is assigned in the bundle. Assess backports by code change rather than version string alone because distribution kernels may include the fix independently.

Mitigation direction

  • Update to a vendor-supported kernel containing the referenced stable fix.
  • Prioritize multi-user or untrusted-workload systems where local users can exercise relevant kernel functionality.
  • If immediate updating is impossible, consult the Linux distribution vendor for supported mitigations.
  • Reboot into the updated kernel and remove exposure to superseded vulnerable kernels.

Validation and detection

  • Inventory running kernel versions across Linux hosts.
  • Compare distribution kernel builds with the referenced upstream stable commits.
  • Confirm the active kernel after patching and rebooting.
  • Run vendor-approved regression tests covering fprobe, ftrace, and BPF functionality.
  • Monitor kernel logs for protection faults involving fprobe_handler.
Prepared
Confidence
medium
Sources
5

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2023-53557 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/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
0ADP providers
4Source links

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
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2023-53557Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/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.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux5b0ab78998e32564a011b14c4c7f9c81e2d42b9d, 5b0ab78998e32564a011b14c4c7f9c81e2d42b9d, 5b0ab78998e32564a011b14c4c7f9c81e2d42b9dunaffected
LinuxLinux5.18, 0, 6.1.40, 6.4.5, 6.5affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.