# CVE-2026-79592: libxls out-of-bounds read in xls_dumpSummary

Source: https://junglewise.ai/threats/cve-2026-79592-libxls-out-of-bounds-read-in-xls-dumpsummary  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-10. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-79592 · Severity: high · CVSS 7.5 · Published 2026-09-10

libxls is a library used to parse Excel spreadsheet files in binary XLS format. A maliciously crafted XLS file can trigger an out-of-bounds memory read in the summary information parser, causing the application to crash or potentially leak sensitive data from memory. Any application using libxls to open untrusted XLS files is at risk.

Technologies: [Libxls](https://junglewise.ai/threats/technologies/libxls). Vendors: [Libxls](https://junglewise.ai/threats/vendors/libxls).

## Quick answers

**Is CVE-2026-79592 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-79592 being exploited in the wild.

**How severe is CVE-2026-79592?** High severity, with a CVSS score of 7.5, published 10 September 2026.

**Which products and versions are affected?** Libxls 1.6.3.

**Is there a fix for CVE-2026-79592?** A patch was published on 2026-08-21: Patch merged in PR #165 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-79592 attacked?** It is attacked over the network or with local access.

**Am I affected by CVE-2026-79592?** Check whether you run Libxls at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

This is an out-of-bounds read vulnerability (CWE-125) in the xls_dumpSummary() function, which parses OLE SummaryInformation and DocumentSummaryInformation property sets. The vulnerable code performs pointer arithmetic using file-controlled offsets (plist->sectionOffset and secHead->numProperties) without bounds validation, allowing an attacker to craft an XLS file with malicious offset values that cause the parser to read memory outside the allocated summary buffer. Attack vector is network/local (file opening); no authentication is required. The vulnerability enables information disclosure (memory leak) or denial of service (crash). A patch was merged to validate offsets before use.

## Affected products

- libxls libxls 1.6.3

## Timeline

- 2026-09-10: disclosed
- 2026-08-21: patched: Patch merged in PR #165

## References

- [https://github.com/libxls/libxls/issues/162](https://github.com/libxls/libxls/issues/162)
- [https://github.com/libxls/libxls/pull/165/changes/6eed8bc1d51d6649faebab0184b21ab8768d8fa6](https://github.com/libxls/libxls/pull/165/changes/6eed8bc1d51d6649faebab0184b21ab8768d8fa6)

## Related threats

- [libxls heap-buffer-overflow and use-after-free in xls_getCSS](https://junglewise.ai/threats/cve-2026-79591-libxls-heap-buffer-overflow-and-use-after-free-in-xls-getcss)
- [libxls use-of-uninitialized memory in xls_parseWorkBook](https://junglewise.ai/threats/cve-2026-26825-libxls-use-of-uninitialized-memory-in-xls-parseworkbook)
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