# CVE-2026-115819: GNU C Library wide scanf one-byte buffer overflow

Source: https://junglewise.ai/threats/cve-2026-115819-calling-the-wide-scanf-family-of-functions-swscanf-fwscanf  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-11. Updated: 2026-11-11  
License: CC BY 4.0 with a link back

CVE-2026-115819 · Severity: medium · CVSS 4.8 · Published 2026-11-11

The GNU C Library's wide character scanf functions (swscanf, fwscanf, wscanf and variants) write an extra null byte past the end of a buffer when converting wide character strings to narrow character arrays. An attacker can craft input that exactly fills a properly-sized destination buffer, causing one byte of data corruption or process crash.

Technologies: [Gnu C Library (glibc)](https://junglewise.ai/threats/technologies/c-library-glibc). Vendors: [Gnu](https://junglewise.ai/threats/vendors/gnu).

## Quick answers

**Is CVE-2026-115819 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-115819 being exploited in the wild.

**How severe is CVE-2026-115819?** Medium severity, with a CVSS score of 4.8, published 11 November 2026.

**Which products and versions are affected?** Gnu C Library (glibc) 2.2 to 2.44.

**Is there a fix for CVE-2026-115819?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-115819 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-115819?** Check whether you run Gnu C Library (glibc) 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

The wide scanf family writes multibyte sequences converted from wide characters into caller-provided char arrays. When a %s or %[ conversion without the 'l' length modifier completes, the functions unconditionally append a second null byte after the terminating null already written by __wcrtomb, overflowing a buffer sized per C standard requirements. The overflow is triggered only when converted input and terminator exactly fill the destination; the overflowing byte is always null.

## Affected products

- GNU C Library (glibc) 2.2 to 2.44

## Timeline

- 2026-11-11: disclosed

## References

- [https://sourceware.org/bugzilla/show_bug.cgi?id=34989](https://sourceware.org/bugzilla/show_bug.cgi?id=34989)
- [https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0027](https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0027)

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- [GNU C Library SHIFT_JISX0213 converter hang in iconv](https://junglewise.ai/threats/cve-2026-77117-gnu-c-library-shift-jisx0213-converter-hang-in-iconv)