CVE-2026-19499: Heap Overflow (CVSS 7.7)

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.

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CVSS v3.1 Score

7.7

HIGH

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

EPSS — Exploit Prediction

0.0038

Probability of exploitation

0.31%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-122 CWE-122

References

Other References

https://sourceware.org/bugzilla/show_bug.cgi?id=34510 https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0017

Frequently Asked Questions

What is CVE-2026-19499? +

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. It has a CVSS v3.1 base score of 7.7 (HIGH).

How severe is CVE-2026-19499? +

CVE-2026-19499 has a CVSS v3.1 score of 7.7 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0038, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-19499? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-19499