GHSA-829p-mc9m-7xhr · Severity: high — Calling the ungetwc function on a FILE stream with wide characters encoded in a character set...
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.
Conclusion & alert: CVE-2026-5928 is rated Exploit Available (50.6/100): CVSS High severity, with low exploitation likelihood (EPSS 0.05%). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
| EDB-ID | Source | Kind | Published | Link |
|---|---|---|---|---|
| — | nvd_ref | exploit_tag | Exploit-DB ↗ |
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-05-22 | 0.02% | 0.05% | +0.03% |
| 2 | 2026-04-21 | — | 0.02% | — |
Full EPSS history (2 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 7.5 | 3.1 | HIGH |
|
3.9 | 3.6 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
GHSA-829p-mc9m-7xhr · Severity: high — Calling the ungetwc function on a FILE stream with wide characters encoded in a character set...
| vendor | priority | summary | link |
|---|---|---|---|
debian
|
not yet assigned | CVE-2026-5928 not yet assigned priority: Debian including 1 source packages (glibc), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 5. | https://security-tracker.debian.org/tracker/CVE-2026-5928 |
suse
|
medium | — | https://www.suse.com/security/cve/CVE-2026-5928/ |
ubuntu
|
medium | CVE-2026-5928 medium priority: Ubuntu including 2 source packages (eglibc, glibc), 14 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): needs-triage 10, DNE 4. | https://ubuntu.com/security/CVE-2026-5928 |
| URL | Tags |
|---|---|
| https://sourceware.org/bugzilla/show_bug.cgi?id=33998 | Exploit Issue Tracking |