CVE-2026-23845VulnerabilityPublished 19 Jan 2026Updated 20 Jan 2026

CVE-2026-23845: axllent mailpit · Server-Side Request Forgery (SSRF)

Affects axllent mailpitSource CVE Database V5

Not known to be exploited · CVSS 5.8 Medium : upgrade to 1.28.3 when convenient.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 3.1 base score

5.8Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 37% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.28.3

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: Low
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade mailpit and axllent/mailpit to 1.28.3.

Affected software

Product	Affected	Fixed in
axllentmailpit	Affected <1.28.3	Fixed in 1.28.3
GitHubaxllent/mailpit`pkg:github/axllent/mailpit`Other threats	Affected <1.28.3	Fixed in 1.28.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

1. Upgrade Mailpit to version 1.28.3 or later immediately to apply the official fix. 2. Restrict outbound HTTP/HTTPS requests from the Mailpit server to only trusted destinations using network-level controls such as firewall rules or proxy whitelisting. 3. Implement input validation or sanitization on email content before processing to detect and block suspicious external CSS links. 4. Isolate the Mailpit environment in a segmented network zone with limited access to sensitive internal resources to minimize impact if exploited. 5. Monitor Mailpit server logs for unusual outbound requests or access patterns indicative of SSRF exploitation attempts. 6. Educate development and QA teams about the risks of processing untrusted email content and enforce secure handling practices. 7. Regularly review and update security policies related to developer tools and testing environments to include SSRF threat awareness.

Description

Mailpit is an email testing tool and API for developers. Versions prior to 1.28.3 are vulnerable to Server-Side Request Forgery (SSRF) via HTML Check CSS Download. The HTML Check feature (`/api/v1/message/{ID}/html-check`) is designed to analyze HTML emails for compatibility. During this process, the `inlineRemoteCSS()` function automatically downloads CSS files from external `<link rel="stylesheet" href="...">` tags to inline them for testing. Version 1.28.3 fixes the issue.

Impact

For European organizations, the SSRF vulnerability in Mailpit poses a risk of unauthorized internal network reconnaissance and potential data leakage. Since Mailpit is used primarily by developers and QA teams for email testing, exploitation could allow attackers to pivot from the email testing environment to internal services that are otherwise inaccessible externally. This could expose sensitive internal APIs, databases, or configuration endpoints, leading to confidentiality breaches. Although the vulnerability does not directly impact system integrity or availability, the information gained could facilitate further attacks. The lack of authentication and user interaction requirements increases the risk of automated exploitation, especially in environments where Mailpit is exposed to untrusted email inputs or external networks. Organizations handling sensitive or regulated data (e.g., financial, healthcare, or government sectors) are particularly at risk of compliance violations if internal data is exposed. The medium severity score indicates a moderate but non-negligible threat that should be addressed promptly to prevent escalation.

CWE-918Server-Side Request Forgery (SSRF) (opens in a new tab)
Base weaknessCWE Top 25 (2025): #22OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
OWASP Cheat Sheets
Server Side Request Forgery Prevention (opens in a new tab)
Unvalidated Redirects and Forwards (opens in a new tab)
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.6.1 (opens in a new tab)
V5.2.6 (opens in a new tab)
Attack patterns
Server Side Request Forgery (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Jan 2026, 19:58 UTC

WeaknessesCWE-918

Technical details

References

Community reviews

Related threats