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A newly disclosed flaw in the Windows Defender Firewall Service could allow privileged attackers to read sensitive portions of system memory.
The vulnerability “… allows an authorized attacker to disclose information locally,” said Microsoft in its advisory.
Why a Low CVSS Still Matters
Despite its relatively low CVSS score of 4.4, the flaw underscores ongoing memory-safety risks in core Windows components.
Affected systems include Windows Server 2025, Windows Server 2022, and Windows 11 (23H2, 24H2, and 25H2) across both x64 and ARM64 architectures.
The out-of-bounds read could allow attackers with elevated privileges to extract memory fragments without user interaction, potentially exposing credentials, configuration data, or other sensitive information when paired with additional compromise techniques.
While Microsoft says exploitation is unlikely and no active attacks or proof-of-concept (PoC) code have surfaced, memory disclosure bugs are often leveraged as building blocks in multi-stage attacks, especially in environments with weak privileged-access controls.
Inside the Windows Defender Memory Bug
The vulnerability, tracked as CVE-2025-62468, stems from a boundary-checking error in the Windows Defender Firewall Service that allows the service to read data beyond the bounds of an intended memory buffer.
Because the affected component operates with elevated system privileges, a local attacker who already has high-level access can deliberately trigger the flaw and read arbitrary portions of heap memory.
This behavior does not allow direct code execution, but it can expose sensitive in-memory data that the service was never intended to return.
Exploitation requires local access and elevated privileges, and it does not involve user interaction, which significantly narrows the attack surface.
However, this also reinforces a broader security reality: privileged accounts remain prime targets for attackers.
Even limited memory disclosure bugs can be valuable in post-compromise scenarios, helping adversaries leak credentials, uncover configuration details, weaken exploit mitigations like ASLR, or chain the flaw with other vulnerabilities to enable more reliable and stealthy attacks.
Reducing Risk From Memory Disclosure
Memory disclosure flaws rarely operate in isolation, but they can become powerful enablers once an attacker has elevated access.
Reducing risk means assuming some level of compromise and focusing on limiting what attackers can see, reuse, or chain together.
- Enable Credential Guard and LSASS protections to reduce the value of any memory fragments that could be exposed post-compromise.
- Apply exploit mitigation policies (such as ASR rules and enhanced memory protections) to limit how memory disclosure flaws can be chained with other exploits.
- Segment and monitor privileged access paths, ensuring admin accounts are used only from hardened jump hosts or Privileged Access Workstations (PAWs).
- Increase visibility into post-exploitation behavior, including unusual service interactions, memory inspection tools, or debugging utilities on endpoints.
- Audit firewall service dependencies and configurations to reduce unnecessary exposure or misuse of elevated components.
- Regularly rotate credentials and secrets on systems with high privilege to limit the usefulness of any leaked memory data.
- Conduct tabletop or purple-team exercises focused on post-compromise scenarios, where attackers already have elevated access and chain low-severity flaws.
Taken together, these practices help organizations limit the practical impact of memory disclosure issues and strengthen resilience against post-compromise activity.
Why Low-Severity Bugs Still Matter
CVE-2025-62468 highlights a recurring reality in modern security: even mature, widely deployed defensive components can still harbor subtle memory-handling flaws.
As attackers increasingly chain low-severity issues into effective intrusion paths, small weaknesses can compound into real risk — especially in environments with shared administrative access or limited visibility into privileged activity.
This vulnerability reinforces the need for stronger privilege separation, improved memory safety, and continuous monitoring of high-privilege behavior rather than relying on patching alone.
With no system truly secure, zero-trust principles help minimize exposure and lateral movement.
