CVE-2019-20056

Exp

stb_image.h (aka the stb image loader) 2.23, as used in libsixel and other products, has an assertion failure in stbi__shiftsigned.

Published: 2019-12-29 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2019-20056 is rated High Exploit Risk (61.1/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.94%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2019-20056

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2019-20056

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.47% 0.94% +0.47%
2 2025-11-21 0.31% 0.47% +0.16%
3 2025-11-18 — 0.31% —

Full EPSS history (12 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2019-20056

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2019-20056

OS Trackers for CVE-2019-20056

vendor priority summary link
debian low CVE-2019-20056 low priority: Debian including 2 source packages (libsixel, libstb), 10 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 9, open 1. https://security-tracker.debian.org/tracker/CVE-2019-20056
ubuntu medium CVE-2019-20056 medium priority: Ubuntu including 1 source packages (libsixel), 18 status rows across 18 suites (bionic, disco, eoan, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 11, needs-triage 4, ignored 2, DNE 1. https://ubuntu.com/security/CVE-2019-20056

Affected software / configurations for CVE-2019-20056

Vendor Product Version Raw CPE
nothings stb_image.h 2.23 cpe:2.3:a:nothings:stb_image.h:2.23:*:*:*:*:*:*:*

References for CVE-2019-20056

URL Tags
https://github.com/saitoha/libsixel/issues/126 Exploit Third Party Advisory
cvelogic Threat Intelligence