CVE-2026-94056: Exim before 4.100.1, when Proxy-Protocol is used with an attacker-controlled proxy, allows attackers to read c

Q: How do I fix CVE-2026-94056?

exim: upgrade to 4.100.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-94056 being exploited?

CVE-2026-94056 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-94056 affect?

CVE-2026-94056 affects exim. Severity is high (CVSS 7.5). Exim before 4.100.1, when Proxy-Protocol is used with an attacker-controlled proxy, allows attackers to read certain uninitialized data from stack memory.

Q: How urgent is CVE-2026-94056?

Priority 35/100. High severity; Remotely exploitable, no login, no user action

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-94056 is a high-severity flaw (CVSS 7.5) affecting exim. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Exim before 4.100.1, when Proxy-Protocol is used with an attacker-controlled proxy, allows attackers to read certain uninitialized data from stack memory.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 85%)
CISA exploited list	No
Weakness	CWE-908
Published	2026-09-19
Last modified	2026-09-24

Publisher (CNA): MITRE · Vendor: exim

Last updated 2026-09-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-19 23:17 UTCPublished CVE record published
2026-09-24 20:45 UTCUpdated Record last modified

exim exim UPGRADE

Affected: < 4.100.1

Fixed in: 4.100.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 4.100.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade exim

Note

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

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-2026-94056?

exim: upgrade to 4.100.1. Exact commands for each OS are on this page.

Is CVE-2026-94056 being exploited?

CVE-2026-94056 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-2026-94056 affect?

CVE-2026-94056 affects exim. Severity is high (CVSS 7.5). Exim before 4.100.1, when Proxy-Protocol is used with an attacker-controlled proxy, allows attackers to read certain uninitialized data from stack memory.

How urgent is CVE-2026-94056?

Priority 35/100. High severity; Remotely exploitable, no login, no user action

Software pages

Exim vulnerabilities

Related CVEs

CVE-2026-94054 HIGH 7.0 UPGRADE Exim before 4.100.1, when Proxy-Protocol is used with an attacker-controlled proxy, has an out-of-bounds write
CVE-2026-94055 LOW 3.7 UPGRADE Exim before 4.100.1, when certain non-default TLS settings are used with GnuTLS, has a use-after-free.
CVE-2026-94057 MEDIUM 4.0 UPGRADE Exim before 4.100.1 allows SMTP smuggling in which the received message does not match any sent message, and i

References

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