CVE-2021-39534: An issue was discovered in libslax through v0.22.1

Q: How do I fix CVE-2021-39534?

libslax: upgrade to newer than 0.22.1. Exact commands for each OS are on this page.

Q: Is CVE-2021-39534 being exploited?

CVE-2021-39534 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-2021-39534 affect?

CVE-2021-39534 affects libslax. Severity is high (CVSS 8.8). An issue was discovered in libslax through v0.22.1. slaxIsCommentStart() in slaxlexer.c has a heap-based buffer overflow.

Q: How urgent is CVE-2021-39534?

Priority 53/100. High severity; Public exploit reference

This month

HIGH 8.8UPGRADE

CVE-2021-39534 is a high-severity flaw (CVSS 8.8) affecting libslax. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in libslax through v0.22.1. slaxIsCommentStart() in slaxlexer.c has a heap-based buffer overflow.

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.3% (top 30%)
CISA exploited list	No
Weakness	CWE-787
Published	2021-09-20
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: juniper

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

juniper libslax UPGRADE

Affected: <= 0.22.1

Fixed in: newer than 0.22.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 0.22.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libslax

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-2021-39534?

libslax: upgrade to newer than 0.22.1. Exact commands for each OS are on this page.

Is CVE-2021-39534 being exploited?

CVE-2021-39534 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-2021-39534 affect?

CVE-2021-39534 affects libslax. Severity is high (CVSS 8.8). An issue was discovered in libslax through v0.22.1. slaxIsCommentStart() in slaxlexer.c has a heap-based buffer overflow.

How urgent is CVE-2021-39534?

Priority 53/100. High severity; Public exploit reference

Software pages

Juniper Junos vulnerabilities

Related CVEs

CVE-2021-39533 HIGH 8.8 UPGRADE An issue was discovered in libslax through v0.22.1
CVE-2021-39532 MEDIUM 6.5 UPGRADE An issue was discovered in libslax through v0.22.1
CVE-2021-39531 HIGH 8.8 UPGRADE An issue was discovered in libslax through v0.22.1
CVE-2019-1010232 MEDIUM 6.5 DOWNGRADE Juniper juniper/libslax libslax latest version (as of commit 084ddf6ab4a55b59dfa9a53f9c5f14d192c4f8e5 Commits

References

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