CVE-2021-42716: An issue was discovered in stb stb_image.h 2.27. The PNM loader incorrectly interpreted 16-bit PGM files as 8-bit when converting to RGBA, leading to ...

Description

An issue was discovered in stb stb_image.h 2.27. The PNM loader incorrectly interpreted 16-bit PGM files as 8-bit when converting to RGBA, leading to a buffer overflow when later reinterpreting the result as a 16-bit buffer. An attacker could potentially have crashed a service using stb_image, or read up to 1024 bytes of non-consecutive heap data without control over the read location.

Metrics

CVSS 3.1

7.1/10

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

EPSS Probability

1.36%

68.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-120

Affected Software

Vendor	Product	Versions
Nothings	Stb Image.H	2.27
Fedoraproject	Fedora	33
Fedoraproject	Fedora	34
Fedoraproject	Fedora	35

References

Timeline

Published: Oct 21, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-42716?

An issue was discovered in stb stb_image.h 2.27. The PNM loader incorrectly interpreted 16-bit PGM files as 8-bit when converting to RGBA, leading to a buffer overflow when later reinterpreting the result as a 16-bit buffer. An attacker could potentially have crashed a service using stb_image, or read up to 1024 bytes of non-consecutive heap data without control over the read location.

How severe is CVE-2021-42716?

CVE-2021-42716 has a CVSS score of 7.1/10 (HIGH severity). The EPSS model estimates a 1.36% probability of exploitation in the next 30 days.

How do I fix CVE-2021-42716?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.