CVE-2020-8794: OpenSMTPD before 6.6.4 allows remote code execution because of an out-of-bounds read in mta_io in mta_session.c for multi-line replies.
Noroxi assessment
Priority: This week (action score 66/100)
- A ready-made attack module is public (Metasploit); exploiting it takes no special expertise.
- Public proof-of-concept code exists (Exploit-DB); there is no record of exploitation in the wild.
- Probability of exploitation in the next 30 days: 88.9% (FIRST EPSS); higher than 99.7% of all records.
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- Fixed version: opensmtpd-extras (Alpine:v3.13) 6.6.4-r0; opensmtpd (Debian:10) 6.0.3p1-5+deb10u4; opensmtpd (Debian:12) 6.6.4p1-1.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Don’t wait for the next maintenance window. Upgrade to opensmtpd-extras (Alpine:v3.13) 6.6.4-r0; opensmtpd (Debian:10) 6.0.3p1-5+deb10u4; opensmtpd (Debian:12) 6.6.4p1-1 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
OpenSMTPD before 6.6.4 allows remote code execution because of an out-of-bounds read in mta_io in mta_session.c for multi-line replies. Although this vulnerability affects the client side of OpenSMTPD, it is possible to attack a server because the server code launches the client code during bounce handling.
- Published
- Feb 25, 2020
- Updated
- Jun 16, 2026
- EPSS
- 88.9% · 99th percentile
- CWE
- CWE-125
Report tools
Action score
66
This week
Don’t wait for the next maintenance window.
- CVSS
- 39 / 40 · 9.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 27 / 30 · 88.9%
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- Weaponized exploit exists
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| opensmtpd | opensmtpd | cpe:2.3:a:opensmtpd:opensmtpd |
| canonical | ubuntu linux | cpe:2.3:o:canonical:ubuntu_linux |
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- canonical ubuntu linux18.04
- canonical ubuntu linux19.10
- debian debian linux10.0
- debian debian linux9.0
- fedoraproject fedora31
- fedoraproject fedora32
- opensmtpd opensmtpdbefore 6.6.4
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.13 | opensmtpd-extras | before 6.6.4-r0 | 6.6.4-r0 |
| Debian:10 | opensmtpd | before 6.0.3p1-5+deb10u4 | 6.0.3p1-5+deb10u4 |
| Debian:12 | opensmtpd | before 6.6.4p1-1 | 6.6.4p1-1 |
| Debian:9 | opensmtpd | before 6.0.2p1-2+deb9u3 | 6.0.2p1-2+deb9u3 |
Same product
opensmtpd: all recordsOther highest-scoring records for the same primary product.
- CVE-2023-29323ascii_load_sockaddr in smtpd in OpenBSD before 7.1 errata 024 and 7.2 before errata 020, and OpenSMTPD Portable before 7.0.0-portable commit31Monitor
- CVE-2020-35680smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote attackers to cause a denial of service (NULL pointe31Monitor
- CVE-2020-35679smtpd/table.c in OpenSMTPD before 6.8.0p1 lacks a certain regfree, which might allow attackers to trigger a "very significant" memory leak v31Monitor
Published before and after this one in the same product
- ← EarlierCVE-2020-8793Feb 25, 2020 · OpenSMTPD before 6.6.4 allows local users to read arbitrary files (e.g., on some Linux distributions) because of a combination of an untrust18Monitor
- Later →CVE-2025-62875Nov 20, 2025 · Local DoS in OpenSMTPD via UNIX domain socket smtpd.sock27Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| alpine:opensmtpd-extras | 6.6.4-r0 · Alpine:v3.13 | Package registry (OSV) |
| debian:opensmtpd | 6.6.4p1-1 · Debian:12 | Package registry (OSV) |
Exploit status
Weaponized
A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.
Evidence
- Metasploit module ×1
- Exploit-DB entry ×2
Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.
| Source | Kind | Date |
|---|---|---|
| Exploit-DB entry | local | 2020-03-09 |
| Exploit-DB entry | remote | 2020-02-26 |
| Metasploit module | exploit/unix/local/opensmtpd_oob_read_lpeOpenSMTPD OOB Read Local Privilege Escalationexploit | 2020-02-24 |
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- Metasploit-2 d
- Published
- First PoCsame day
- TodayNov 7, 2026+2447 d
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-20-115 · Feb 26, 2020(OpenSMTPD Sunucu Güvenlik Güncellemesi)
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-125 · Out-of-bounds ReadCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
ATT&CK techniques
—
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (6 more)Show less
- seclists.org/fulldisclosure/2020/Feb/32
- www.openwall.com/lists/oss-security/2020/03/01/1
- www.openwall.com/lists/oss-security/2020/03/01/2
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OPH4QU4DNVHA7ACFXMYFCEP5PSXXPN4E/
- usn.ubuntu.com/4294-1/
- www.openbsd.org/security.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.