CVE-2026-5928
Buffer Under-Read in GNU C Library ungetwc Causes Data Leak
Publication date: 2026-04-20
Last updated on: 2026-04-23
Assigner: GNU C Library
Description
Description
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| gnu | glibc | to 2.43 (inc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-127 | The product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations prior to the targeted buffer. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability occurs in the GNU C Library version 2.43 or earlier when the ungetwc function is called on a FILE stream containing wide characters encoded in a character set where single byte and multi-byte character encodings overlap.
Due to a bug in the wide character pushback implementation, ungetwc operates on the wrong buffer pointer, which can cause it to read bytes before the allocated buffer.
This can lead to either unintentional disclosure of adjacent heap data or a program crash if the buffer pointer is uninitialized.
The issue requires a special character encoding with overlapping single and multi-byte representations, which does not occur in standard Unicode character sets.
How can this vulnerability impact me? :
The vulnerability can cause a program crash or potentially expose neighboring data in memory unintentionally.
This means that sensitive information stored adjacent in the heap memory could be disclosed if exploited under the right conditions.