Static buffer overflow in deprecated nis_local_principal

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Summary

CVECVE-2026-5928
StatePUBLISHED
Assignerglibc
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-20 21:16:36 UTC
Updated2026-04-20 21:16:36 UTC
DescriptionCalling 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.

Risk And Classification

Problem Types: CWE-127 | CWE-127 CWE-127 Buffer under-read

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA The GNU C Library Glibc affected 2.1.1-89 2.43 custom Not specified

References

ReferenceSourceLinkTags
sourceware.org/bugzilla/show_bug.cgi 3ff69d7a-14f2-4f67-a097-88dee7810d18 sourceware.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Rocket Ma (en)

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