PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-39824 golang.org/x/sys CVE debrief

CVE-2026-39824 describes an integer overflow vulnerability in the Go programming language's `NewNTUnicodeString` function. The function fails to validate that input string lengths fit within the maximum size of an NTUnicodeString structure (a 16-bit byte count). When provided with an oversized string, the function silently truncates the data rather than returning an error, which could lead to unexpected behavior in applications relying on complete string processing. The vulnerability was published on May 22, 2026, and last modified on May 26, 2026. The issue affects Go's Windows-specific syscall handling and has been assigned the Go vulnerability ID GO-2026-5024.

Vendor
golang.org/x/sys
Product
golang.org/x/sys/windows
CVSS
LOW 3.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-22
Original CVE updated
2026-07-23
Advisory published
2026-05-22
Advisory updated
2026-07-23

Who should care

Organizations running Go applications on Windows platforms, particularly those processing user-controlled strings through Windows NT APIs. Security teams should prioritize patching development and production Go toolchains. Developers using syscall.NewNTUnicodeString directly should review their code for assumptions about string completeness

Technical summary

The `NewNTUnicodeString` function in Go's syscall package for Windows does not properly validate input string lengths against the 16-bit maximum size limit of the NTUnicodeString structure. When a string exceeds 65535 bytes, the length calculation overflows, resulting in silent truncation rather than an error return. This behavior violates the principle of fail-safe defaults and may cause security-relevant logic errors in applications that assume complete string processing. The vulnerability is specific to Go's Windows syscall implementation and does not affect other platforms

Defensive priority

medium

Recommended defensive actions

  • Review Go security advisory GO-2026-5024 for patch availability and affected versions
  • Update Go installations to patched versions once released by the Go team
  • Audit applications using syscall.NewNTUnicodeString for potential truncation-related logic errors
  • Monitor Windows-specific Go applications for unexpected string handling behavior
  • Subscribe to golang-announce for security update notifications

Evidence notes

The vulnerability description is sourced from the NVD record, which references official Go security advisories. The vendor identification as Go is based on reference domain evidence from golang.org sources, though marked as requiring review due to the 'unknown-vendor' classification in source data. The vulnerability is specifically tied to Windows NT Unicode string handling in Go's syscall package

Sources and references

Verified primary and authoritative sources

  • CVE-2026-39824 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-39824

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-39824 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-39824

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.