CVE-2026-5928

CVE Enrichment

CVSS: 7.5 HIGH
EPSS: 0.49%
EPSS Percentile: 41.14%
CISA KEV: Not listed

Description

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.

Technical Details

CVSS Version: 3.1
CNA / NVD Source: 3ff69d7a-14f2-4f67-a097-88dee7810d18
Published: 21-Apr-2026 04:16
Last Modified: 14-Jul-2026 20:19
EPSS Date: 2026-10-20
CWE: CWE-127

CVSS Vector


            CVSS:3.1                            AV:N /
                            AC:L /
                            PR:N /
                            UI:N /
                            S:U /
                            C:N /
                            I:N /
                            A:H

Affected Products / Versions

gnu / glibc Source: NVD CPE · affected
Version / affected range: * · through (inclusive) 2.43
cpe:2.3:a:gnu:glibc:*:*:*:*:*:*:*:*

References

Last enrichment sync: 01-Nov-2026 19:19
Sources: NVD · FIRST EPSS · CISA KEV
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Reported Context (1)

glibc itself picked up fixes for a buffer overflow and a buffer underflow, CVE-2026-5928 and CVE-2026-5450, plus a change to keep it working with Linux 7.0 headers. Debian 13.7 Bundles 92 Security Advisories and Updates 106 Packages

CVE (19)

Products (18)

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