Security readout for executives and security teams
Plain-English summary
CVE-2020-28024 affects Exim mail servers before 4.94.2. The flaw can let an unauthenticated remote attacker execute arbitrary commands. For organizations running Exim on internet-facing mail gateways, this is a business-critical exposure because mail servers are commonly reachable from untrusted networks.
Executive priority
Handle urgently for any exposed Exim server. The potential impact is remote command execution without authentication, and mail infrastructure is often externally reachable. Patch validation should be prioritized over broad investigation unless indicators suggest compromise.
Technical view
The issue is a buffer underwrite in Exim's SMTP handling. The source says smtp_ungetc was intended to push back characters, but could push back non-character error codes such as EOF. Exim 4 before 4.94.2 is identified as vulnerable.
Likely exposure
Exposure is most likely on systems running Exim before 4.94.2, especially SMTP services reachable from the internet or untrusted networks. The provided CVE metadata lacks precise CPEs, package names, and distribution backport details.
Exploitation context
The provided bundle does not show CISA KEV listing or active exploitation evidence. The public description does state unauthenticated remote attackers may execute arbitrary commands, so absence of exploitation evidence should not be treated as low risk.
Researcher notes
The source bundle is limited: no CVSS vector, CWE, CPEs, or active exploitation source is provided. Analysis relies mainly on the CVE description and Exim advisory reference. Validate affectedness against actual Exim builds and vendor backport status.
Mitigation direction
- Upgrade Exim to 4.94.2 or later where applicable.
- Check operating system vendor advisories for backported Exim fixes.
- Restrict SMTP exposure to required networks where business allows.
- Prioritize internet-facing mail gateways and relay hosts.
- Review vendor guidance before applying compensating controls.
Validation and detection
- Inventory all hosts running Exim and record exact versions.
- Confirm whether distribution packages include a backported fix.
- Identify Exim services reachable from the internet or untrusted networks.
- Review mail server logs for abnormal SMTP handling errors.
- Track remediation evidence for each exposed mail server.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2020-28024 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://www.exim.org/static/doc/security/CVE-2020-qualys/CVE-2020-28024-UNGET.txtCVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.