CVE-2019-3940: Advantech WebAccess 8.3.4 is vulnerable to file upload attacks via unauthenticated RPC call

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2019-3940 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 8.3.4 is vulnerable to file upload attacks via unauthenticated RPC call. An unauthenticated, remote attacker can use this vulnerability to execute arbitrary code.

Why this priority

Critical severity
EPSS top 9%: very likely to be exploited
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	4.1% (top 9%)
CISA exploited list	No
Weakness	CWE-434
Published	2019-04-09
Last modified	2026-06-17

Publisher (CNA): Tenable Network Security, Inc. · Vendor: advantech

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

Am I affected?

Timeline

2019-04-09 16:29 UTCPublished CVE record published
2026-06-17 02:35 UTCUpdated Record last modified

advantech webaccess DOWNGRADE

Affected: 8.3.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.3.4

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 8.3.4 (Debian / Ubuntu)

apt-cache madison webaccess sudo apt install webaccess=<VERSION_BEFORE_8.3.4> sudo apt-mark hold webaccess

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

dnf --showduplicates list webaccess sudo dnf downgrade webaccess-<VERSION_BEFORE_8.3.4> sudo dnf versionlock add webaccess

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-2019-3940?

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

Is CVE-2019-3940 being exploited?

CVE-2019-3940 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-2019-3940 affect?

CVE-2019-3940 affects webaccess. Severity is critical (CVSS 9.8). Advantech WebAccess 8.3.4 is vulnerable to file upload attacks via unauthenticated RPC call. An unauthenticated, remote attacker can use this vulnerability to execute arbitrary code.

How urgent is CVE-2019-3940?

Priority 62/100. Critical severity; EPSS top 9%: very likely to be exploited; 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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