Security readout for executives and security teams
Plain-English summary
Mailpit before 1.28.3 can let a remote sender alter email headers handled by its SMTP server. This is mainly an integrity issue for development and testing email workflows, not a data theft or system takeover issue based on current sources.
Executive priority
Treat as a moderate-priority patch for developer infrastructure. Prioritize faster remediation if Mailpit is reachable outside trusted environments or supports security-sensitive testing workflows where manipulated email headers could mislead users or systems.
Technical view
The SMTP server’s validation for RCPT TO and MAIL FROM addresses used an insufficient regex that failed to exclude carriage returns and line feeds in a character class. This allowed SMTP header injection or corruption of existing headers. Fixed in Mailpit 1.28.3.
Likely exposure
Exposure is most relevant where Mailpit’s SMTP server is reachable by untrusted users, shared development networks, CI systems, or internet-facing test environments. Internal-only developer instances have lower business impact but should still be updated.
Exploitation context
No active exploitation is reported in the provided sources, and this CVE is not listed as KEV. The issue is network-reachable, low-complexity, requires no authentication or user interaction, and affects message integrity rather than confidentiality or availability.
Researcher notes
This maps to CWE-93 and CWE-150. The public advisory attributes impact to regex validation failure in SMTP envelope address handling. The cited commit and v1.28.3 release are the authoritative fix references. No public source in the bundle confirms exploitation in the wild.
Mitigation direction
- Upgrade Mailpit to version 1.28.3 or later.
- Restrict Mailpit SMTP access to trusted hosts and networks.
- Avoid exposing development Mailpit instances to the public internet.
- Review vendor advisory and release notes for deployment-specific guidance.
Validation and detection
- Inventory all Mailpit deployments and container images.
- Confirm each instance is running Mailpit 1.28.3 or later.
- Check whether the SMTP service is reachable from untrusted networks.
- Review CI and developer tooling that sends mail through Mailpit.
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.
CWE-150: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-93: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-23829 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
- Medium
- CVSS
- 5.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
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 vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/axllent/mailpit/security/advisories/GHSA-54wq-72mp-cq7cCVE reference · x_refsource_CONFIRM
- https://github.com/axllent/mailpit/commit/36cc06c125954dec6673219dafa084e13cc14534CVE reference · x_refsource_MISC
- https://github.com/axllent/mailpit/releases/tag/v1.28.3CVE 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.
Improper Neutralization of Escape, Meta, or Control Sequences
Improper Neutralization of Escape, Meta, or Control Sequences represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Improper Neutralization of CRLF Sequences ('CRLF Injection')
Improper Neutralization of CRLF Sequences ('CRLF Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.