Critical severity · published Apr 20, 2026
CVE-2026-5450
scanf %mc off-by-one heap buffer overflow
9.8
CVSS
0.5%
EPSS
No
On KEV
Description
Calling 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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 43% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
GL
glibc · The GNU C Library
2.7 · source: vendor, NVD
SS
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.5 before V3.1.6; V3.1.5 before V3.1.6 · source: CISA
SS
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP · Siemens
V3.1.5 before V3.1.6; V3.1.5 before V3.1.6 · source: CISA
SS
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.5 before V3.1.6 · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-5450
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-5450
Third Party Advisory
https://inbox.sourceware.org/libc-announce/b11f0003-6ec1-4bd6-b9de-9e38a4efeca3@redhat.com/T/#u
Exploit
https://sourceware.org/bugzilla/show_bug.cgi?id=CVE-2026-5450
cert-portal.siemens.com
https://cert-portal.siemens.com/productcert/html/ssa-082556.html
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