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Fencer Vulns
high 7.1

CVE-2021-42716 json

An issue was discovered in stb stb_image.h 2.27.

published 2021-10-21 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-29676

cvss
7.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.5%
EPSS 1.5% chance of exploitation in 30 days, percentile 73%
public exploits
0
none known

Summary

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.

Patch / fix

  • libstb Debian 14, Debian 13 0.0~git20230129.5736b15+ds-1

debian advisories DEBIAN-CVE-2021-42716

  • zxing-cpp SLE Workstation Extension 12 SP5, SLE Software Development Kit 12 SP5 1.2.0-8.6.1
  • zxing-cpp SLE Workstation Extension 15 SP3, SLE Module for Package Hub 15 SP3 1.2.0-9.7.1

suse advisories SUSE-SU-2022:0163-1SUSE-SU-2022:0157-1

  • zxing-cpp openSUSE Leap 15.3 1.2.0-9.7.1
  • stb Package Hub 15 SP3, openSUSE Leap 15.3 2.32.1549563867.59e9702-bp153.2.3.1

opensuse advisories openSUSE-SU-2022:0157-1openSUSE-SU-2022:0018-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-42716 updated cvss 8.0

stb: heap-based buffer overflow in stb_image PNM loader

  • Red Hat Enterprise Linux 6 clutter
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 cogl, compat-libcogl12, compat-libcogl-pango12 Red Hat Enterprise Linux 8 cogl
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.46% chance of exploitation in the next 30 days, higher than 73% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/nothings/stb/issues/1166 referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/nothings/stb/issues/1225 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
NVD 2.0 5.8 AV:N/AC:M/Au:N/C:P/I:N/A:P

Classification

Weakness
  • CWE-120 Buffer Copy without Checking Size of Input

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.