CVE-2021-3131: The Web server in 1C:Enterprise 8 before 8.3.17.1851 sends base64 encoded credentials in the creds URL paramet

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HIGH 7.5REMOTEUPGRADE

CVE-2021-3131 is a high-severity flaw (CVSS 7.5) affecting 1c\. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The Web server in 1C:Enterprise 8 before 8.3.17.1851 sends base64 encoded credentials in the creds URL parameter.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 38%)
CISA exploited list	No
Weakness	CWE-326
Published	2021-01-13
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: 1c

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

Am I affected?

Timeline

2021-01-13 16:15 UTCPublished CVE record published
2026-06-17 04:04 UTCUpdated Record last modified

1c 1c\ UPGRADE

Affected: >= 8.0 and < 8.3.17.1851

Fixed in: 8.3.17.1851

Safe to downgrade to: a release before 8.0

1. Check installed version

apt-cache policy 1c || rpm -q 1c || 1c --version

2. UPGRADE to 8.3.17.1851 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade 1c

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade 1c

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 8.0 (Debian / Ubuntu)

apt-cache madison 1c sudo apt install 1c=<VERSION_BEFORE_8.0> sudo apt-mark hold 1c

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list 1c sudo dnf downgrade 1c-<VERSION_BEFORE_8.0> sudo dnf versionlock add 1c

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-2021-3131?

1c\: upgrade to 8.3.17.1851. Exact commands for each OS are on this page.

Is CVE-2021-3131 being exploited?

CVE-2021-3131 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-2021-3131 affect?

CVE-2021-3131 affects 1c\. Severity is high (CVSS 7.5). The Web server in 1C:Enterprise 8 before 8.3.17.1851 sends base64 encoded credentials in the creds URL parameter.

How urgent is CVE-2021-3131?

Priority 47/100. High severity; Remotely exploitable, no login, no user action

References

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