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CVE-2026-43185
critical
CVSS 9.8
Vulnerability in linux (CVE-2026-43185)
Summary
vulnerability in linux (CVE-2026-43185). Successful exploitation can lead to full system takeover.
AI summary openai / gpt-4o
A critical bug in the Linux kernel can allow unauthorized manipulation of system data when specific data is supplied. This issue is similar to Heartbleed seen in OpenSSL, which allowed attackers to adversely affect systems. Installing the updated kernel is necessary to fix this vulnerability.
In the Linux kernel, the function `smb_direct_prepare_negotiation()` mishandles type casting of certain variables, allowing a deliberately crafted `preferred_send_size` to trigger a heap buffer overflow. An attacker achieves this by sending a second message with a large value (>1420 bytes). The issue is addressed by modifying the type casting. The fix is available through a kernel update, detail which can be found in specific commits on `git.kernel.org`.
❓ What is the problem
A heap buffer overflow vulnerability in the Linux kernel's smb_direct_prepare_negotiation() function due to improper type casting.
📍 Affected scope
smb_direct_prepare_negotiation() function within the ksmbd of the Linux kernel.
🔥 Severity
Critical, with a CVSS score of 9.8 indicating high potential impact through remote exploitation without user interaction.
🔧 How to fix
Update the Linux kernel to a version that includes the patch described in the relevant git commits.
🛡️ Workaround
No known workaround is specified in the material; updating the kernel is recommended.
🔍 Detection
Monitor for large messages (>1420 bytes) in ksmbd transactions or utilize updated kernel logs for unusual activity.
Related past incidents Similar incidents extracted from past CVEs
Heartbleed was a similar vulnerability affecting OpenSSL that exposed data in memory due to improper input validation.
A heap-based buffer overflow in Sudo that could allow privilege escalation.
A remote code execution vulnerability in Apache Log4j due to improper input validation.
If this happens at your company Expected impact per business scenario
📌 Enterprise environments using Linux servers for critical operations.
Compromise of server control through remote code execution without authentication.
📌 IoT devices running Linux under embedded systems.
Potential exploitation leading to device control or data theft.
📌 Cloud service providers utilizing Linux-based infrastructure.
Service disruptions or data breaches due to kernel vulnerabilities.
Recommended action
Organizations should urgently update affected Linux kernel versions to mitigate this critical vulnerability.
Response Actions (7 steps)
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.依存マニフェストで影響コンポーネントを特定する。
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7Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 3 と同じログクエリでアラート再発が無いか継続監視。
References
- web https://git.kernel.org/stable/c/55abc475d096da4a5356b6efb0cfdc6156bc1550
- web https://git.kernel.org/stable/c/6b4f875aac344cdd52a1f34cc70ed2f874a65757
- web https://git.kernel.org/stable/c/ceae058eb707ddd0d68f0872f9d9f23b7c30c37b
- web https://nvd.nist.gov/vuln/detail/CVE-2026-43185
- web https://github.com/advisories/GHSA-vcg7-gx5w-x44c