CVE-2021-33023: Advantech WebAccess versions 9.02 and prior are vulnerable to a heap-based buffer overflow, which may allow an

Q: How do I fix CVE-2021-33023?

webaccess: upgrade to newer than 9.0.2. Exact commands for each OS are on this page.

Q: Is CVE-2021-33023 being exploited?

CVE-2021-33023 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-2021-33023 affect?

CVE-2021-33023 affects webaccess. Severity is critical (CVSS 9.8). Advantech WebAccess versions 9.02 and prior are vulnerable to a heap-based buffer overflow, which may allow an attacker to remotely execute code.

Q: How urgent is CVE-2021-33023?

Priority 60/100. Critical severity; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2021-33023 is a critical-severity flaw (CVSS 9.8) affecting webaccess. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Advantech WebAccess versions 9.02 and prior are vulnerable to a heap-based buffer overflow, which may allow an attacker to remotely execute code.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.3% (top 16%)
CISA exploited list	No
Weakness	CWE-122, CWE-787
Published	2021-10-18
Last modified	2026-06-17

Publisher (CNA): ICS-CERT · Vendor: advantech

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

Am I affected?

Timeline

2021-10-18 13:15 UTCPublished CVE record published
2026-06-17 03:54 UTCUpdated Record last modified

advantech webaccess UPGRADE

Affected: <= 9.0.2

Fixed in: newer than 9.0.2

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 9.0.2 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade webaccess

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-2021-33023?

webaccess: upgrade to newer than 9.0.2. Exact commands for each OS are on this page.

Is CVE-2021-33023 being exploited?

CVE-2021-33023 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-2021-33023 affect?

CVE-2021-33023 affects webaccess. Severity is critical (CVSS 9.8). Advantech WebAccess versions 9.02 and prior are vulnerable to a heap-based buffer overflow, which may allow an attacker to remotely execute code.

How urgent is CVE-2021-33023?

Priority 60/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Advantech vulnerabilities

Related CVEs

CVE-2023-4215 MEDIUM 6.5 DOWNGRADE Advantech WebAccess version 9.1.3 contains an exposure of sensitive information to an unauthorized actor vulne
CVE-2023-2866 HIGH 7.3 DOWNGRADE If an attacker can trick an authenticated user into loading a maliciously crafted .zip file onto Advantech We
CVE-2021-38408 CRITICAL 9.8 UPGRADE A stack-based buffer overflow vulnerability in Advantech WebAccess Versions 9.02 and prior caused by a lack of
CVE-2021-38389 CRITICAL 9.8 UPGRADE Advantech WebAccess versions 9.02 and prior are vulnerable to a stack-based buffer overflow, which may allow a
CVE-2021-34540 MEDIUM 6.1 DOWNGRADE Advantech WebAccess 8.4.2 and 8.4.4 allows XSS via the username column of the bwRoot.asp page of WADashboard.

References

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