CVE-2020-28247: The lettre library through 0.10.0-alpha for Rust allows arbitrary sendmail option injection via transport/send

This month

MEDIUM 5.3REMOTEUPGRADE

CVE-2020-28247 is a medium-severity flaw (CVSS 5.3) affecting lettre. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The lettre library through 0.10.0-alpha for Rust allows arbitrary sendmail option injection via transport/sendmail/mod.rs.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.5% (top 25%)
CISA exploited list	No
Published	2020-11-12
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: lettre

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

Am I affected?

Timeline

2020-11-12 18:15 UTCPublished CVE record published
2026-06-17 03:10 UTCUpdated Record last modified

lettre lettre UPGRADE

Affected: >= 0.8.0 and <= 0.8.3 · >= 0.9.0 and <= 0.9.5 · 0.7.0 · 0.10.0 alpha1 · 0.10.0 alpha2 · 0.10.0 alpha3

Fixed in: newer than 0.9.5

Safe to downgrade to: a release before 0.7.0

1. Check installed version

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

2. UPGRADE to newer than 0.9.5 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade lettre

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 0.7.0 (Debian / Ubuntu)

apt-cache madison lettre sudo apt install lettre=<VERSION_BEFORE_0.7.0> sudo apt-mark hold lettre

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

dnf --showduplicates list lettre sudo dnf downgrade lettre-<VERSION_BEFORE_0.7.0> sudo dnf versionlock add lettre

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-2020-28247?

lettre: upgrade to newer than 0.9.5. Exact commands for each OS are on this page.

Is CVE-2020-28247 being exploited?

CVE-2020-28247 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-2020-28247 affect?

CVE-2020-28247 affects lettre. Severity is medium (CVSS 5.3). The lettre library through 0.10.0-alpha for Rust allows arbitrary sendmail option injection via transport/sendmail/mod.rs.

How urgent is CVE-2020-28247?

Priority 42/100. Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-38189 CRITICAL 9.8 UPGRADE An issue was discovered in the lettre crate before 0.9.6 for Rust

References

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