CVE-2026-19499

Buffer overflow in strfmon and strfmon_l right-justification padding

Published Sep 14, 2026 CVSS 3.1 · 7.7 High EPSS < 1% KEV · Not listed
Description
Calling strfmon and strfmon_l in the GNU C Library version 2.38 to 2.44 can write past the end of the caller-supplied output buffer when a conversion uses right-justified width padding.

Exploitation requires an application code path that calls strfmon or strfmon_l with right-justified width padding into a destination buffer that is large enough for the padding to succeed but too small for the internal memmove call. The field width or format may be attacker-influenced or a fixed susceptible pattern in the caller.

At the time of publication, no network-facing application impact is known.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Ubuntu USN Ubuntu USN USN-8737-1 GNU C Library vulnerabilities
Ubuntu USN Ubuntu USN USN-8737-2 GNU C Library vulnerabilities
History
Type Values Removed Values Added
Description A flaw was found in glibc. The strfmon and strfmon_l functions are vulnerable to a buffer overflow when processing right-justified width padding. This occurs because an incorrect length is used for an internal memory operation, causing data to be written beyond its intended buffer. An attacker could exploit this by providing specially crafted input, potentially leading to arbitrary code execution or other severe impacts. Calling strfmon and strfmon_l in the GNU C Library version 2.38 to 2.44 can write past the end of the caller-supplied output buffer when a conversion uses right-justified width padding. Exploitation requires an application code path that calls strfmon or strfmon_l with right-justified width padding into a destination buffer that is large enough for the padding to succeed but too small for the internal memmove call. The field width or format may be attacker-influenced or a fixed susceptible pattern in the caller. At the time of publication, no network-facing application impact is known.
Title glibc: Buffer Overflow in strfmon right-justification padding Buffer overflow in strfmon and strfmon_l right-justification padding
Weaknesses CWE-122
References
Metrics cvssV3_1

{'score': 6.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:H'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

cvssV3_1

{'score': 7.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:H'}

Type Values Removed Values Added
First Time appeared Gnu
Gnu glibc
Vendors & Products Gnu
Gnu glibc
Type Values Removed Values Added
Description A flaw was found in glibc. The strfmon and strfmon_l functions are vulnerable to a buffer overflow when processing right-justified width padding. This occurs because an incorrect length is used for an internal memory operation, causing data to be written beyond its intended buffer. An attacker could exploit this by providing specially crafted input, potentially leading to arbitrary code execution or other severe impacts.
Title glibc: Buffer Overflow in strfmon right-justification padding
Weaknesses CWE-787
References
Metrics threat_severity

None

cvssV3_1

{'score': 6.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:H'}

threat_severity

Moderate

Weaknesses

Sources

Status
PUBLISHED
Assigner
glibc
Published
Updated
Sep 14, 2026, 7:40 PM
Reserved
Aug 10, 2026, 6:42 PM
Status
Awaiting Analysis
Published
Sep 14, 2026, 6:17 PM
Modified
Sep 18, 2026, 6:17 PM
Severity
Moderate
Public date
Aug 25, 2026, 7:32 AM