scanf %mc off-by-one heap buffer overflow

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Summary

CVECVE-2026-5450
StatePUBLISHED
Assignerglibc
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-20 21:16:36 UTC
Updated2026-04-23 15:33:34 UTC
DescriptionCalling the scanf family of functions with a %mc (malloc'd character match) in the GNU C Library version 2.7 to version 2.43 with a format width specifier with an explicit width greater than 1024 could result in a one byte heap buffer overflow.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from ADP

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

EPSS: 0.000490000 probability, percentile 0.152730000 (date 2026-04-26)

Problem Types: CWE-122 | CWE-787 | CWE-122 CWE-122 Heap-based buffer overflow

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Gnu Glibc All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA The GNU C Library Glibc affected 2.7 * custom Not specified

References

ReferenceSourceLinkTags
inbox.sourceware.org/libc-announce/[email protected]/T 3ff69d7a-14f2-4f67-a097-88dee7810d18 inbox.sourceware.org Third Party Advisory
sourceware.org/bugzilla/show_bug.cgi 134c704f-9b21-4f2e-91b3-4a467353bcc0 sourceware.org Exploit, Issue Tracking
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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