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GlibcFramework / library · Gnu

CVE-2026-5928

HIGH · 7.5 CVSS v3.1 Published 2026-04-20
Fix available
A fix is available. Upgrade to after 2.43 or later.
See remediation →
84/100
Remediation priority · High
Public exploit Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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 summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
GlibcFramework / library
Affected:<= 2.43

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 2.43
Recommended fix High confidence

glibc 2.44 or later

  1. 1. Identify the glibc version currently installed on affected systems by running: ldd --version or /lib/x86_64-linux-gnu/libc.so.6
  2. 2. For systems using package managers: Update the glibc package to version 2.44 or later (e.g., apt-get update && apt-get install libc6 on Debian/Ubuntu, or yum update glibc on RHEL/CentOS)
  3. 3. For systems building from source: Download glibc version 2.44 or newer from http://ftp.gnu.org/gnu/glibc/ and rebuild
  4. 4. After updating, restart any running services that use the updated glibc to ensure they load the new library
  5. 5. Verify the new version is loaded: ldd --version should show version 2.44 or later
Caveat Major glibc upgrades can cause compatibility issues with older binaries or libraries that depend on specific glibc behaviors; test thoroughly in a staging environment before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

We can identify the exact fixed release, upgrade, and verify it in staging — typical engagement from $1,950. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-5928 in production — separate from our analysis above.

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What this is

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