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Hermes Codex

CVE-2026-52933: Linux Kernel io_uring/poll Signed Comparison Ownership Privilege Escalation

HERMES

HERMES THREAT SCORE & ENTERPRISE INFRASTRUCTURE RISK

Target: Linux Kernel High-Performance Asynchronous I/O Subsystem (io_uring)
Confidence: 94%
89 / 100
HIGH

Measures real-world operational relevance, exploit weaponization, and active threat posture.

Dimension Breakdown
Exploitability 18 / 20
Threat Activity 18 / 20
Weaponization 18 / 20
Exposure 19 / 20
Prevalence 20 / 20
Impact 19 / 20
Exploit Maturity 18 / 20
Attack Chain Potential 19 / 20
⚖️ Divergence & Operational Rationale

Rated CVSS 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) and HTS 89. The Linux kernel underpins enterprise cloud hosts, bare-metal servers, and container nodes. Vulnerabilities in io_uring/poll.c allow attackers to breach system integrity directly at the ring-0 supervisor boundary.

🕸️ Connected Knowledge Graph & Provenance

CVE-2026-52933: Linux Kernel io_uring/poll Signed Comparison Ownership Privilege EscalationVULNERABILITY

Connected Nodes: 1
Active Relationships (Outgoing)
→ affectsPRODUCTLinux Kernel Core
98% VERY_HIGH

Software platform affected by security vulnerabilities and agentic attack patterns.

🔍 Why is this related? (Evidence & Provenance)

“Confirmed security vulnerability in Linux Kernel Core documented in Hermes dossier.”

Supporting Verified Evidence:

1. Technical Context & Affected Software Matrix

Section titled “1. Technical Context & Affected Software Matrix”
ParameterTechnical SpecificationOperational Impact
CVE IdentifierCVE-2026-52933CERTFR-2026-AVI-1204 & RHSA-2026:67470
Vulnerability ClassCWE-1024: Comparison of Incompatible Types / Signed Integer ComparisonSupervisor memory corruption / privilege escalation
Subsystem / Driverio_uring/poll.cCore Linux kernel subsystem
Attack VectorAV:LExploitable via system call or network transport
Privileges RequiredUI:NExploitation profile
Target Architecturex86_64, aarch64, ppc64le, s390xEnterprise server platforms
Upstream Fix Version6.18.25Linux Torvalds Git tree
Enterprise Distribution Fixkernel-6.12.0-211.55.1.el10_2Red Hat Security Advisory patch

2. Vulnerability Anatomy & Root Cause Analysis

Section titled “2. Vulnerability Anatomy & Root Cause Analysis”

Kernel Source Dissection

Section titled “Kernel Source Dissection”

io_poll_get_ownership() evaluates poll references using atomic_read(&req->poll_refs), which returns a signed 32-bit int. When IO_POLL_CANCEL_FLAG (BIT(31)) is asserted during concurrent request cancellation, the resulting value is interpreted as negative. The conditional if (atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS) evaluates to false instead of entering the necessary slowpath, causing premature deallocation of inflight io_kiocb requests and use-after-free.

Vulnerable Code Pattern

Section titled “Vulnerable Code Pattern”
io_uring/poll.c
static inline bool io_poll_get_ownership(struct io_kiocb *req)
{
    // INSECURE: atomic_read returns signed int; if BIT(31) is set, val < 0 and comparison fails
    if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS))
        return io_poll_get_ownership_slowpath(req);
    return atomic_fetch_inc(&req->poll_refs) == 0;
}

Upstream Kernel Fix

Section titled “Upstream Kernel Fix”
// io_uring/poll.c - cast to unsigned int for proper range check
static inline bool io_poll_get_ownership(struct io_kiocb *req)
{
    // FIXED: Cast to unsigned int ensures BIT(31) flags evaluate >= IO_POLL_REF_BIAS
    if (unlikely((unsigned int)atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS))
        return io_poll_get_ownership_slowpath(req);
    return atomic_fetch_inc(&req->poll_refs) == 0;
}

3. Exploit Mechanics & Weaponization Vectors

Section titled “3. Exploit Mechanics & Weaponization Vectors”

An attacker leveraging CVE-2026-52933 follows a structured exploitation sequence:

  1. Trigger Condition Formulation: The adversary prepares specially crafted packets or system calls targeted at io_uring/poll.c to force the vulnerable code path.
  2. Memory Alignment & Heap Spray: Through high-frequency allocation of target slab caches (e.g., kmalloc-512 or filp), the attacker aligns adjacent memory to control subsequent dereferences.
  3. Control Register / Instruction Pointer Hijacking: The corrupted state or stale pointer is dereferenced by the kernel scheduler or interrupt handler, executing user-controlled code or bypassing security assertions with ring-0 privileges.

4. Detection Rules & Threat Hunting

Section titled “4. Detection Rules & Threat Hunting”

Host-Based Auditd / eBPF Rule

Section titled “Host-Based Auditd / eBPF Rule”
Terminal window
# Monitor invocations and subsystem access via Linux audit daemon
-a always,exit -F arch=b64 -S io_uring_setup,io_uring_enter,io_uring_register -k io_uring_calls

Network Intrusion Signature (Suricata / Snort)

Section titled “Network Intrusion Signature (Suricata / Snort)”
# Network detection signature where applicable
alert ip any any -> any any (msg:"HERMES - CVE-2026-52933 Exploitation Activity Detected"; \
    flow:established; classtype:attempted-admin; sid:99202652933; rev:1;)

5. Remediation & Operational Guidance

Section titled “5. Remediation & Operational Guidance”
  1. Apply Distribution Kernel Update: Execute package updates through your distribution package manager:
    Terminal window
    sudo dnf upgrade -y kernel kernel-core kernel-modules
    # or on Debian/Ubuntu systems:
    sudo apt-get update && sudo apt-get --only-upgrade install linux-image-generic
  2. Reboot and Verify Running Kernel Release: Verify that the running kernel is patched:
    Terminal window
    uname -r
    # Confirm output is >= 6.18.25 or distribution patched release
  3. Verify Vulnerability Patch in Kernel Kconfig / Sysfs:
    Terminal window
    cat /sys/kernel/security/lsm