CVE-2021-39515

Exp

An issue was discovered in libjpeg through 2020021. A NULL pointer dereference exists in the function SampleInterleavedLSScan::ParseMCU() located in sampleinterleavedlsscan.cpp. It allows an attacker to cause Denial of Service.

Published: 2021-09-20 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-39515 is rated Exploit Available (57.1/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.26%). 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-2021-39515

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

Exploit prediction scoring system (EPSS) score for CVE-2021-39515

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 2025-03-30 0.40% 0.26% -0.14%
2 2025-03-29 0.26% 0.40% +0.14%
3 2025-03-17 — 0.26% —

Full EPSS history (8 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-39515

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-2021-39515

OS Trackers for CVE-2021-39515

vendor priority summary link
debian not yet assigned CVE-2021-39515 not yet assigned priority: Debian including 1 source packages (libjpeg), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-39515
ubuntu medium CVE-2021-39515 medium priority: Ubuntu including 4 source packages (libjpeg, libjpeg-turbo, libjpeg6b, libjpeg9), 60 status rows across 15 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 51, DNE 3, ignored 3, needs-triage 2, released 1. https://ubuntu.com/security/CVE-2021-39515

Affected software / configurations for CVE-2021-39515

Vendor Product Version Raw CPE
jpeg libjpeg <= 2020021 cpe:2.3:a:jpeg:libjpeg:*:*:*:*:*:*:*:*

References for CVE-2021-39515

URL Tags
https://github.com/thorfdbg/libjpeg/issues/37 Exploit Issue Tracking Third Party Advisory
cvelogic Threat Intelligence