CVE-2026-45709: Mailpit is an email testing tool and API for developers

This week

MEDIUM 5.8REMOTEUPGRADE

CVE-2026-45709 is a medium-severity flaw (CVSS 5.8) affecting mailpit. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Mailpit is an email testing tool and API for developers. The fix for GHSA-6jxm-fv7w-rw5j (CVE-2026-23845, "Server-Side Request Forgery (SSRF) via HTML Check API"), shipped in mailpit `v1.28.3`, hardened `internal/htmlcheck/css.go::downloadCSSToBytes` with a 5MB size cap, a `text/css` content-type check, login-info stripping in `isValidURL`, and an opt-in `--block-remote-css-and-fonts` config flag — but did not add the IP-filtering dialer that the

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 77%)
CISA exploited list	No
Weakness	CWE-918
Published	2026-07-20
Last modified	2026-10-24

Publisher (CNA): GitHub, Inc. · Vendor: axllent

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-20 16:17 UTCPublished CVE record published
2026-10-24 20:10 UTCUpdated Record last modified

axllent mailpit UPGRADE

Affected: >= 1.28.3 and < 1.30.0

Fixed in: 1.30.0

Safe to downgrade to: a release before 1.28.3

1. Check installed version

apt-cache policy mailpit || rpm -q mailpit || mailpit --version

2. UPGRADE to 1.30.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mailpit

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mailpit

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.28.3 (Debian / Ubuntu)

apt-cache madison mailpit sudo apt install mailpit=<VERSION_BEFORE_1.28.3> sudo apt-mark hold mailpit

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list mailpit sudo dnf downgrade mailpit-<VERSION_BEFORE_1.28.3> sudo dnf versionlock add mailpit

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-45709?

mailpit: upgrade to 1.30.0. Exact commands for each OS are on this page.

Is CVE-2026-45709 being exploited?

CVE-2026-45709 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-45709 affect?

CVE-2026-45709 affects mailpit. Severity is medium (CVSS 5.8). Mailpit is an email testing tool and API for developers. The fix for GHSA-6jxm-fv7w-rw5j (CVE-2026-23845, "Server-Side Request Forgery (SSRF) via HTML Check API"), shipped in mailpit `v1.28.3`, hardened `internal/htmlcheck/css.go::downloadC

How urgent is CVE-2026-45709?

Priority 36/100. Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-45713 HIGH 7.5 UPGRADE Mailpit is an email testing tool and API for developers
CVE-2026-48824 MEDIUM 5.3 UPGRADE Mailpit is an email testing tool and API for developers
CVE-2026-45712 MEDIUM 5.9 UPGRADE Mailpit is an email testing tool and API for developers
CVE-2026-45711 MEDIUM 5.9 UPGRADE Mailpit is an email testing tool and API for developers

References

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