NVD / CVE Program· CNA mitre

CVE-2021-42716: An issue was discovered in stb stb_image.h 2.27.

HighCVSS 7.1 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 28/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 1.4% (FIRST EPSS); higher than 73.8% of all records.
Someone with local access to the system can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
Fixed version: libstb (Debian:13) 0.0~git20230129.5736b15+ds-1; stb (openSUSE:Leap 15.3) 2.32.1549563867.59e9702-bp153.2.3.1; zxing-cpp (openSUSE:Leap 15.3) 1.2.0-9.7.1.

Low priority for now. Upgrade to libstb (Debian:13) 0.0~git20230129.5736b15+ds-1; stb (openSUSE:Leap 15.3) 2.32.1549563867.59e9702-bp153.2.3.1; zxing-cpp (openSUSE:Leap 15.3) 1.2.0-9.7.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Memory safety

Published: Oct 21, 2021
Updated: Jun 17, 2026
EPSS: 1.4% · 73th percentile
CWE: CWE-120

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 28 / 40 · 7.1 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 1.4%

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
nothings	stb image.h	cpe:2.3:a:nothings:stb_image.h
fedoraproject	fedora	cpe:2.3:o:fedoraproject:fedora

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

fedoraproject fedora33
fedoraproject fedora34
fedoraproject fedora35
nothings stb image.h2.27

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	libstb	from 0	—
Debian:13	libstb	before 0.0~git20230129.5736b15+ds-1	0.0~git20230129.5736b15+ds-1
openSUSE:Leap 15.3	stb	before 2.32.1549563867.59e9702-bp153.2.3.1	2.32.1549563867.59e9702-bp153.2.3.1
openSUSE:Leap 15.3	zxing-cpp	before 1.2.0-9.7.1	1.2.0-9.7.1
SUSE:Linux Enterprise Module for Package Hub 15 SP3	zxing-cpp	before 1.2.0-9.7.1	1.2.0-9.7.1
SUSE:Linux Enterprise Software Development Kit 12 SP5	zxing-cpp	before 1.2.0-8.6.1	1.2.0-8.6.1
SUSE:Package Hub 15 SP3	stb	before 2.32.1549563867.59e9702-bp153.2.3.1	2.32.1549563867.59e9702-bp153.2.3.1

Same product

nothings: all records

Other highest-scoring records for the same primary product.

CVE-2023-45666Possible double-free or memory leak in stbi__load_gif_main in stb_image
39Monitor
CVE-2023-45664Double-free in stbi__load_gif_main_outofmem in stb_image
35Monitor
CVE-2022-28042stb_image.h v2.27 was discovered to contain an heap-based use-after-free via the function stbi__jpeg_huff_decode.
35Monitor

Published before and after this one in the same product

← EarlierCVE-2019-20056Dec 29, 2019 · stb_image.h (aka the stb image loader) 2.23, as used in libsixel and other products, has an assertion failure in stbi__shiftsigned.
26Monitor
← EarlierCVE-2021-42715Oct 21, 2021 · An issue was discovered in stb stb_image.h 1.33 through 2.27.
22Monitor
Later →CVE-2022-28041Apr 15, 2022 · stb_image.h v2.27 was discovered to contain an integer overflow via the function stbi__jpeg_decode_block_prog_dc.
27Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
debian:libstb	0.0~git20230129.5736b15+ds-1 · Debian:13	Package registry (OSV)
opensuse:stb	2.32.1549563867.59e9702-bp153.2.3.1 · openSUSE:Leap 15.3	Package registry (OSV)
opensuse:zxing-cpp	1.2.0-9.7.1 · openSUSE:Leap 15.3	Package registry (OSV)
suse:stb	2.32.1549563867.59e9702-bp153.2.3.1 · SUSE:Package Hub 15 SP3	Package registry (OSV)
suse:zxing-cpp	1.2.0-9.7.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP3	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

nothings/stbPR 1223

Not on record for this CVE: EPSS history · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

Someone with local access to the system can trigger it.
No account or password is required.
A user must open a link or visit a page.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Local
Attack complexity: Low
Privileges required: None
User interaction: Required
Scope: Unchanged
Confidentiality impact: High
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-120 · Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

CVSS vector

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

nvd-primary

Root cause

When data is copied, the source length is not compared with the size of the destination buffer. Excess data overwrites adjacent memory.

The bug in code

The whole CWE-120 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1char buf[256];
2memcpy(buf, pkt->data, pkt->len);

Fixed

1char buf[256];
2if (pkt->len > sizeof(buf)) {
3  return -EINVAL;
4}
5memcpy(buf, pkt->data, pkt->len);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

—

Change log (1)

Fix✗ → ✓Sep 28, 2026, 10:47 PM UTC

For records you follow, these changes also arrive as notifications. →

References

github.com/nothings/stb/pull/1223

Show all references (9 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records