CVE-2026-62897 Overview
CVE-2026-62897 is an integer overflow vulnerability in Microsoft .NET Framework. An unauthorized attacker can exploit the flaw to execute code locally on an affected system. Microsoft published the advisory through the Microsoft Security Response Center (MSRC) update guide. The weakness is classified under [CWE-190] Integer Overflow or Wraparound.
Exploitation requires local access, high attack complexity, and user interaction. Successful exploitation impacts confidentiality, integrity, and availability. No public proof-of-concept or in-the-wild exploitation has been reported at the time of publication.
Critical Impact
An attacker who wraps an integer calculation in .NET Framework can trigger memory corruption and execute arbitrary code in the context of the vulnerable process.
Affected Products
- Microsoft .NET Framework (see Microsoft Security Update CVE-2026-62897 for specific version list)
Discovery Timeline
- 2026-08-11 - CVE-2026-62897 published to the National Vulnerability Database (NVD)
- 2026-08-12 - Last updated in NVD database
Technical Details for CVE-2026-62897
Vulnerability Analysis
CVE-2026-62897 stems from an integer overflow or wraparound condition within .NET Framework. The framework performs arithmetic on attacker-influenced values without validating that the result stays within the bounds of the destination type. When the calculation wraps, downstream logic treats the wrapped value as valid, producing undersized buffer allocations or incorrect length checks.
The resulting mismatch between expected and actual sizes leads to memory corruption. An attacker who supplies specially crafted input can convert the corruption into arbitrary code execution in the context of the .NET process. Because the flaw sits inside the framework itself, any managed application that processes attacker-controlled data through the vulnerable code path inherits the risk.
Root Cause
The root cause is missing validation of arithmetic results in a .NET Framework routine that handles length, size, or index calculations. The operation exceeds the range representable by the underlying integer type and wraps to a smaller or negative value. Subsequent allocations or copy operations rely on the wrapped value, breaking memory-safety invariants. Microsoft has not published the specific affected component beyond the CWE-190 classification in the MSRC advisory.
Attack Vector
Exploitation requires local access to the target system and user interaction, such as opening a file or running a program that processes attacker-supplied data through .NET Framework. The high attack complexity indicates that the attacker must win a race, prepare specific memory conditions, or supply carefully constructed input. No privileges are required prior to exploitation. Refer to the Microsoft Security Update CVE-2026-62897 advisory for component-specific details.
No verified proof-of-concept code is available. Public exploit details would be expected to demonstrate an oversized length parameter that wraps during allocation or bounds checking inside the affected .NET Framework component.
Detection Methods for CVE-2026-62897
Indicators of Compromise
- Unexpected child processes spawned by .NET Framework host processes such as w3wp.exe, powershell.exe, or custom managed executables
- Crash dumps referencing managed heap corruption, access violations in clr.dll or mscorwks.dll, or Windows Error Reporting entries tied to .NET applications
- Files delivered to endpoints that invoke .NET deserialization or parsing routines shortly before anomalous process activity
Detection Strategies
- Hunt for anomalous process lineage where a .NET application launches shells, script interpreters, or LOLBins immediately after handling untrusted input
- Alert on Windows Event Log entries in the Application log with source .NET Runtime reporting unhandled exceptions or CLR crashes
- Monitor for endpoints missing the CVE-2026-62897 patch across the fleet using vulnerability management data
Monitoring Recommendations
- Enable EDR behavioral telemetry on process creation, module loads, and memory allocations within .NET host processes
- Aggregate crash telemetry centrally and triage repeated CLR faults on the same host as potential exploitation attempts
- Track exposure by correlating installed .NET Framework versions with Microsoft's fixed-version list from MSRC
How to Mitigate CVE-2026-62897
Immediate Actions Required
- Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-62897 to all systems running affected .NET Framework versions
- Prioritize patching on multi-user systems, developer workstations, and servers that process untrusted files
- Restrict local logon and file-delivery paths that allow attackers to stage inputs consumed by .NET applications
Patch Information
Microsoft has released a security update through the MSRC update guide. The patch corrects the arithmetic validation logic in the affected .NET Framework component. Administrators should deploy the update through Windows Update, WSUS, Microsoft Update Catalog, or their standard patch management tooling. Confirm the update installed by checking the .NET Framework version and Microsoft's published KB numbers for the applicable Windows release.
Workarounds
- No official workaround is listed in the MSRC advisory; patching is the supported remediation
- Reduce exposure by enforcing least privilege and application allowlisting to limit which users can execute untrusted .NET workloads
- Constrain untrusted input flowing into .NET services with input validation and sandboxing where feasible until the patch is deployed
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
