CVE-2020-12872: yaws_config.erl in Yaws through 2.0.2 and/or 2.0.7 loads obsolete TLS ciphers, as demonstrated by ones that al

Routine

MEDIUM 5.5WATCHLISTUPGRADE

CVE-2020-12872 is a medium-severity flaw (CVSS 5.5) affecting yaws. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

yaws_config.erl in Yaws through 2.0.2 and/or 2.0.7 loads obsolete TLS ciphers, as demonstrated by ones that allow Sweet32 attacks, if running on an Erlang/OTP virtual machine with a version less than 21.0.

Why this priority

Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 67%)
CISA exploited list	No
Weakness	CWE-326
Published	2020-05-15
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: yaws

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

Am I affected?

Timeline

2020-05-15 19:15 UTCPublished CVE record published
2026-06-17 02:52 UTCUpdated Record last modified

yaws yaws UPGRADE

Affected: >= 2.0.2 and <= 2.0.6

Fixed in: newer than 2.0.6

Safe to downgrade to: a release before 2.0.2

1. Check installed version

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

2. UPGRADE to newer than 2.0.6 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade yaws

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 2.0.2 (Debian / Ubuntu)

apt-cache madison yaws sudo apt install yaws=<VERSION_BEFORE_2.0.2> sudo apt-mark hold yaws

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

dnf --showduplicates list yaws sudo dnf downgrade yaws-<VERSION_BEFORE_2.0.2> sudo dnf versionlock add yaws

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-2020-12872?

yaws: upgrade to newer than 2.0.6. Exact commands for each OS are on this page.

Is CVE-2020-12872 being exploited?

CVE-2020-12872 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-2020-12872 affect?

CVE-2020-12872 affects yaws. Severity is medium (CVSS 5.5). yaws_config.erl in Yaws through 2.0.2 and/or 2.0.7 loads obsolete TLS ciphers, as demonstrated by ones that allow Sweet32 attacks, if running on an Erlang/OTP virtual machine with a version less than 21.0.

How urgent is CVE-2020-12872?

Priority 38/100. Public exploit reference; On your watchlist

Related CVEs

CVE-2020-24916 CRITICAL 9.8 UPGRADE MITIGATE CGI implementation in Yaws web server versions 1.81 to 2.0.7 is vulnerable to OS command injection.
CVE-2020-24379 CRITICAL 9.8 UPGRADE MITIGATE WebDAV implementation in Yaws web server versions 1.81 to 2.0.7 is vulnerable to XXE injection.
CVE-2017-10974 HIGH 7.5 DOWNGRADE Yaws 1.91 allows Unauthenticated Remote File Disclosure via HTTP Directory Traversal with /%5C../ to port 8080
CVE-2016-1000108 MEDIUM 6.1 UPGRADE MITIGATE yaws before 2.0.4 does not attempt to address RFC 3875 section 4.1.18 namespace conflicts and therefore does n
CVE-2011-4350 MEDIUM 6.5 DOWNGRADE MITIGATE Yaws 1.91 has a directory traversal vulnerability in the way certain URLs are processed

References

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