CVE-2019-10735: In Claws Mail 3.14.1, an attacker in possession of S/MIME or PGP encrypted emails can wrap them as sub-parts w

Routine

MEDIUM 4.3WATCHLISTDOWNGRADE

CVE-2019-10735 is a medium-severity flaw (CVSS 4.3) affecting mail. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In Claws Mail 3.14.1, an attacker in possession of S/MIME or PGP encrypted emails can wrap them as sub-parts within a crafted multipart email. The encrypted part(s) can further be hidden using HTML/CSS or ASCII newline characters. This modified multipart email can be re-sent by the attacker to the intended receiver. If the receiver replies to this (benign looking) email, they unknowingly leak the plaintext of the encrypted message part(s) back to

Why this priority

Public exploit reference
On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	4.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Weakness	CWE-319
Published	2019-04-07
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: claws-mail

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2019-04-07 15:29 UTCPublished CVE record published
2026-06-17 02:11 UTCUpdated Record last modified

claws-mail mail DOWNGRADE

Affected: 3.14.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.14.1

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.14.1 (Debian / Ubuntu)

apt-cache madison mail sudo apt install mail=<VERSION_BEFORE_3.14.1> sudo apt-mark hold mail

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list mail sudo dnf downgrade mail-<VERSION_BEFORE_3.14.1> sudo dnf versionlock add mail

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-2019-10735?

mail: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-10735 being exploited?

CVE-2019-10735 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-2019-10735 affect?

CVE-2019-10735 affects mail. Severity is medium (CVSS 4.3). In Claws Mail 3.14.1, an attacker in possession of S/MIME or PGP encrypted emails can wrap them as sub-parts within a crafted multipart email. The encrypted part(s) can further be hidden using HTML/CSS or ASCII newline characters. This modi

How urgent is CVE-2019-10735?

Priority 37/100. Public exploit reference; On your watchlist

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References

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