Status: UPDATED | Advisory ID: CVE-2026-5928
| CVE | CVE-2026-5928 |
| CVSS Score / Version | 7.5 (High) / CVSS v3.1 |
| Updated | 2026-07-14 |
| CVSS Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| CVSS Prose | attack vector is network; attack complexity is low; privileges required is none; user interaction is none; scope is unchanged; confidentiality impact is none; integrity impact is none; availability impact is high. |
| Affected products | Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP, Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP, and The GNU C Library glibc |
| Classified as | CWE-127 (Buffer Under-read) |
| Vendor | Product | Affected Versions | Patch Status |
|---|---|---|---|
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP | ||
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP | ||
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP | ||
| The GNU C Library | glibc |
| Subsystems | General OT |
| Sectors | Multiple |
Calling the ungetwc function on a FILE stream with wide characters encoded in a character set that has overlaps between its single byte and multi-byte character encodings, in the GNU C Library version 2.43 or earlier, may result in an attempt to read bytes before an allocated buffer, potentially resulting in unintentional disclosure of neighboring data in the heap, or a program crash.
A bug in the wide character pushback implementation (_IO_wdefault_pbackfail in libio/wgenops.c) causes ungetwc() to operate on the regular character buffer (fp->_IO_read_ptr) instead of the actual wide-stream read pointer (fp->_wide_data->_IO_read_ptr). The program crash may happen in cases where fp->_IO_read_ptr is not initialized and hence points to NULL. The buffer under-read requires a special situation where the input character encoding is such that there are overlaps between single byte representations and multibyte representations in that encoding, resulting in spurious matches. The spurious match case is not possible in the standard Unicode character sets. (NVD)
Monitor Siemens's and The GNU C Library's web pages for any future patch releases.
| Source | Reference |
|---|---|
| NVD | https://nvd.nist.gov/vuln/detail/CVE-2026-5928 |
| CVE | https://www.cve.org/CVERecord?id=CVE-2026-5928 |