CVE-2021-38189
SMTP command injection in lettre
An issue was discovered in the lettre crate before 0.9.6 for Rust. In an e-mail message body, an attacker can place a . character after two <CR><LF> sequences and then inject arbitrary SMTP commands.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
An issue was discovered in the lettre crate before 0.9.6 for Rust. In an e-mail message body, an attacker can place a . character after two <CR><LF> sequences and then inject arbitrary SMTP commands.
- Record
CVE-2021-38189- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 7.5 High
AV:N/AC:L/Au:N/C:P/I:P/A:P - Weakness
- CWE-77
- Updated
- 2026-11-02
CVE List No score
An issue was discovered in the lettre crate before 0.9.6 for Rust. In an e-mail message body, an attacker can place a . character after two <CR><LF> sequences and then inject arbitrary SMTP commands.
- Record
CVE-2021-38189- Updated
- 2026-11-02
EUVDEUVD-2021-1485 No score
An issue was discovered in the lettre crate before 0.9.6 for Rust. In an e-mail message body, an attacker can place a . character after two <CR><LF> sequences and then inject arbitrary SMTP commands.
- Record
EUVD-2021-1485- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-qc36-q22q-cjw3
SMTP command injection in lettre
Impact
Affected versions of lettre allowed SMTP command injection through an attacker's controlled message body. The module for escaping lines starting with a period wouldn't catch a period that was placed after a double CRLF sequence, allowing the attacker to end the current message and write arbitrary SMTP commands after it.
Fix
The flaw is fixed by correctly handling consecutive CRLF sequences.
References
- Record
GHSA-qc36-q22q-cjw3- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-147
- Updated
- 2026-11-02
OSV
An issue was discovered in the lettre crate before 0.9.6 for Rust. In an e-mail message body, an attacker can place a . character after two <CR><LF> sequences and then inject arbitrary SMTP commands.
- Record
CVE-2021-38189- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVGHSA-qc36-q22q-cjw3
SMTP command injection in lettre
Impact
Affected versions of lettre allowed SMTP command injection through an attacker's controlled message body. The module for escaping lines starting with a period wouldn't catch a period that was placed after a double CRLF sequence, allowing the attacker to end the current message and write arbitrary SMTP commands after it.
Fix
The flaw is fixed by correctly handling consecutive CRLF sequences.
References
- Record
GHSA-qc36-q22q-cjw3- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-147
- Updated
- 2026-11-02
OSVRUSTSEC-2021-0069 No score
SMTP command injection in body
Affected versions of lettre allowed SMTP command injection through an attacker's controlled message body. The module for escaping lines starting with a period wouldn't catch a period that was placed after a double CRLF sequence, allowing the attacker to end the current message and write arbitrary SMTP commands after it.
The flaw is fixed by correctly handling consecutive CRLF sequences.
- Record
RUSTSEC-2021-0069- Updated
- 2026-11-02
Affected products
Affected packages
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-38189 is a critical vulnerability (CVSS 9.8) in Lettre, published May 22, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.49%, the 74th percentile. Fixed in lettre 0.9.6.
References
rustsec.org/advisories/RUSTSEC-2021-0069.html
raw.githubusercontent.com/rustsec/advisory-db/main/crates/lettre/RUSTSEC-2021-0069.md
github.com/lettre/lettre/security/advisories/GHSA-qc36-q22q-cjw3
crates.io/crates/lettre