CVE-2021-39542: An issue was discovered in pdftools through 20200714

Q: How do I fix CVE-2021-39542?

pdftools: upgrade to newer than 2020-07-14. Exact commands for each OS are on this page.

Q: Is CVE-2021-39542 being exploited?

CVE-2021-39542 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-2021-39542 affect?

CVE-2021-39542 affects pdftools. Severity is medium (CVSS 5.5). An issue was discovered in pdftools through 20200714. A NULL pointer dereference exists in the function Font::Size() located in font.cpp. It allows an attacker to cause Denial of Service.

Q: How urgent is CVE-2021-39542?

Priority 37/100. Public exploit reference

Routine

MEDIUM 5.5UPGRADE

CVE-2021-39542 is a medium-severity flaw (CVSS 5.5) affecting pdftools. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in pdftools through 20200714. A NULL pointer dereference exists in the function Font::Size() located in font.cpp. 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	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.6% (top 50%)
CISA exploited list	No
Weakness	CWE-476
Published	2021-09-20
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: pdftools project

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

pdftools project pdftools UPGRADE

Affected: <= 2020-07-14

Fixed in: newer than 2020-07-14

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 2020-07-14 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pdftools

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-2021-39542?

pdftools: upgrade to newer than 2020-07-14. Exact commands for each OS are on this page.

Is CVE-2021-39542 being exploited?

CVE-2021-39542 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-2021-39542 affect?

CVE-2021-39542 affects pdftools. Severity is medium (CVSS 5.5). An issue was discovered in pdftools through 20200714. A NULL pointer dereference exists in the function Font::Size() located in font.cpp. It allows an attacker to cause Denial of Service.

How urgent is CVE-2021-39542?

Priority 37/100. Public exploit reference

Related CVEs

CVE-2021-39543 MEDIUM 5.5 UPGRADE An issue was discovered in pdftools through 20200714
CVE-2021-39541 MEDIUM 5.5 UPGRADE An issue was discovered in pdftools through 20200714
CVE-2021-39540 HIGH 7.8 UPGRADE An issue was discovered in pdftools through 20200714
CVE-2021-39539 MEDIUM 5.5 UPGRADE An issue was discovered in pdftools through 20200714
CVE-2021-39538 MEDIUM 5.5 UPGRADE An issue was discovered in pdftools through 20200714

References

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