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CVE-2026-55783 M2Team CVE debrief

CVE-2026-55783 is a low-severity vulnerability in NanaZip, a 7-Zip derivative for modern Windows. Prior to version 6.5.1749.0, NanaZip's in-house IInArchive handlers unconditionally dereference the caller-supplied Indices array inside Extract when the archive engine signals extract everything by passing Indices as NULL and NumItems as 0xFFFFFFFF. This causes a NULL pointer dereference in the standard Test archive or Extract all code path for various archive types, resulting in a process crash. The issue is fixed in version 6.5.1749.0. This vulnerability has a low severity rating but can still cause crashes if exploited.

Vendor
M2Team
Product
NanaZip
CVSS
LOW 2.4
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-10
Original CVE updated
2026-07-10
Advisory published
2026-07-10
Advisory updated
2026-07-10

Who should care

Users of NanaZip versions prior to 6.5.1749.0 should update to the latest version to prevent potential crashes. This vulnerability is rated as low severity, but users handling archives with NanaZip should still exercise caution. Operators, platform administrators, and security teams should review the vulnerability and implement necessary mitigations.

Technical summary

The vulnerability exists in NanaZip's IInArchive handlers, specifically in the Extract function. When the archive engine requests extraction of all items by passing a NULL Indices array and 0xFFFFFFFF NumItems, the handlers fail to check for this condition and attempt to dereference the NULL pointer, leading to a process crash. This affects various archive types, including WebAssembly, ElectronAsar, Zealfs, Romfs, Ufs, Littlefs, and DotNetSingleFile. The issue can be mitigated by updating to version 6.5.1749.0 or later.

Defensive priority

Low

Recommended defensive actions

  • Update NanaZip to version 6.5.1749.0 or later
  • Use secure archive handling practices
  • Monitor NanaZip for future updates and security advisories
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-07-10T17:17:00.147Z and was last modified on 2026-07-10T19:17:26.120Z. The NVD entry is currently Deferred. The vulnerability affects NanaZip versions prior to 6.5.1749.0. Limited evidence is available, and defenders should verify affected scope and vendor guidance.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-55783 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-55783

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

  • CVE-2026-55783 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-55783

    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.