CVE-2021-40648: In man2html 1.6g, a filename can be created to overwrite the previous size parameter of the next chunk and the

Routine

MEDIUM 5.5DOWNGRADE

CVE-2021-40648 is a medium-severity flaw (CVSS 5.5) affecting man2html. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In man2html 1.6g, a filename can be created to overwrite the previous size parameter of the next chunk and the fd, bk, fd_nextsize, bk_nextsize of the current chunk. The next chunk is then freed later on, causing a freeing of an arbitrary amount of memory.

Why this priority

Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.3% (top 73%)
CISA exploited list	No
Weakness	CWE-20
Published	2022-09-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: man2html project

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

Am I affected?

Timeline

2022-09-09 18:15 UTCPublished CVE record published
2026-06-17 04:07 UTCUpdated Record last modified

man2html project man2html DOWNGRADE

Affected: 1.6g

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.6g

1. Check installed version

apt-cache policy man2html || rpm -q man2html || man2html --version

2. No fixed release: DOWNGRADE to a release before 1.6g (Debian / Ubuntu)

apt-cache madison man2html sudo apt install man2html=<VERSION_BEFORE_1.6g> sudo apt-mark hold man2html

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list man2html sudo dnf downgrade man2html-<VERSION_BEFORE_1.6g> sudo dnf versionlock add man2html

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2021-40648?

man2html: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-40648 being exploited?

CVE-2021-40648 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-2021-40648 affect?

CVE-2021-40648 affects man2html. Severity is medium (CVSS 5.5). In man2html 1.6g, a filename can be created to overwrite the previous size parameter of the next chunk and the fd, bk, fd_nextsize, bk_nextsize of the current chunk. The next chunk is then freed later on, causing a freeing of an arbitrary a

How urgent is CVE-2021-40648?

Priority 31/100. Public exploit reference

Related CVEs

CVE-2021-40647 MEDIUM 5.5 DOWNGRADE In man2html 1.6g, a specific string being read in from a file will overwrite the size parameter in the top chu

References

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