CVE-2026-5450 | scanf %mc off-by-one heap buffer overflow

Exp

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.

Published: 2026-04-20 Last update: 2026-06-17 Assigner: 3ff69d7a-14f2-4f67-a097-88dee7810d18 Source: 3ff69d7a-14f2-4f67-a097-88dee7810d18
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-5450 is rated High Exploit Risk (67.1/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.45%). 1 public exploit reference(s) are indexed (Exploit-DB). 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.

Public exploit references (Exploit-DB) for CVE-2026-5450

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-5450

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 2026-06-15 0.05% 0.45% +0.40%
2 2026-05-22 0.02% 0.05% +0.04%
3 2026-04-21 — 0.02% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-5450

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-5450

GitHub Security Advisory for CVE-2026-5450

GHSA-v898-xg3c-w4rj · Severity: critical — Calling the scanf family of functions with a %mc (malloc'd character match) in the GNU C Library...

OS Trackers for CVE-2026-5450

vendor priority summary link
debian not yet assigned CVE-2026-5450 not yet assigned priority: Debian including 1 source packages (glibc), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 3, resolved 2. https://security-tracker.debian.org/tracker/CVE-2026-5450
suse medium — https://www.suse.com/security/cve/CVE-2026-5450/
ubuntu medium CVE-2026-5450 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-2026-5450

Affected software / configurations for CVE-2026-5450

Vendor Product Version Raw CPE
gnu glibc >= 2.7, <= 2.43 cpe:2.3:a:gnu:glibc:*:*:*:*:*:*:*:*

References for CVE-2026-5450

cvelogic Threat Intelligence