CVE-2021-39516: An issue was discovered in libjpeg through 2020021

Q: How do I fix CVE-2021-39516?

libjpeg: upgrade to newer than 2020021. Exact commands for each OS are on this page.

Q: Is CVE-2021-39516 being exploited?

CVE-2021-39516 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-39516 affect?

CVE-2021-39516 affects libjpeg. Severity is medium (CVSS 6.5). An issue was discovered in libjpeg through 2020021. A NULL pointer dereference exists in the function HuffmanDecoder::Get() located in huffmandecoder.hpp. It allows an attacker to cause Denial of Service.

Q: How urgent is CVE-2021-39516?

Priority 42/100. Public exploit reference

This month

MEDIUM 6.5UPGRADE

CVE-2021-39516 is a medium-severity flaw (CVSS 6.5) affecting libjpeg. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in libjpeg through 2020021. A NULL pointer dereference exists in the function HuffmanDecoder::Get() located in huffmandecoder.hpp. It allows an attacker to cause Denial of Service.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.9% (top 42%)
CISA exploited list	No
Weakness	CWE-476
Published	2021-09-20
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: jpeg

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-09-20 16:15 UTCPublished CVE record published
2026-06-17 04:03 UTCUpdated Record last modified

jpeg libjpeg UPGRADE

Affected: <= 2020021

Fixed in: newer than 2020021

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libjpeg || rpm -q libjpeg || libjpeg --version

2. UPGRADE to newer than 2020021 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libjpeg

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libjpeg

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-39516?

libjpeg: upgrade to newer than 2020021. Exact commands for each OS are on this page.

Is CVE-2021-39516 being exploited?

CVE-2021-39516 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-39516 affect?

CVE-2021-39516 affects libjpeg. Severity is medium (CVSS 6.5). An issue was discovered in libjpeg through 2020021. A NULL pointer dereference exists in the function HuffmanDecoder::Get() located in huffmandecoder.hpp. It allows an attacker to cause Denial of Service.

How urgent is CVE-2021-39516?

Priority 42/100. Public exploit reference

Related CVEs

CVE-2023-37837 MEDIUM 6.5 UPGRADE libjpeg commit db33a6e was discovered to contain a heap buffer overflow via LineBitmapRequester::EncodeRegion
CVE-2023-37836 MEDIUM 6.5 UPGRADE libjpeg commit db33a6e was discovered to contain a reachable assertion via BitMapHook::BitMapHook at bitmaphoo
CVE-2022-37770 MEDIUM 6.5 MITIGATE libjpeg commit 281daa9 was discovered to contain a segmentation fault via LineMerger::GetNextLowpassLine at li
CVE-2022-37769 MEDIUM 6.5 MITIGATE libjpeg commit 281daa9 was discovered to contain a segmentation fault via HuffmanDecoder::Get at huffmandecode
CVE-2022-37768 HIGH 7.5 MITIGATE libjpeg commit 281daa9 was discovered to contain an infinite loop via the component Frame::ParseTrailer.

References

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