An issue was discovered in libjpeg through 2020021.

published 2021-09-20 5y ago modified 2026-06-17 4mo ago also EUVD-2021-25877

cvss: 6.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 58%
public exploits: 0; none known

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

Patch / fix

fixed in 1 distros 1 links 1

jpeg libjpeg 9e

libjpeg Debian 14, Debian 13, Debian 12 0.0~git20200925.f145908-1

debian advisories DEBIAN-CVE-2021-39520

github.com/thorfdbg/libjpeg/issues/34 advisory

Is CVE-2021-39520 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Exploit prediction

0.86% chance of exploitation in the next 30 days, higher than 58% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

github.com https://github.com/thorfdbg/libjpeg/issues/34 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
NVD	2.0	4.3	AV:N/AC:M/Au:N/C:N/I:N/A:P

Classification

Weakness

CWE-476 NULL Pointer Dereference

References

github.com /thorfdbg/libjpeg/issues/34
exploit, issue-tracking, patch, third-party-advisory

Sources

CVE List CVE-2021-39520
NVD CVE-2021-39520

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CPEs and fixed versions use Anchore's correction of NVD's data: Update CPE details.