CVE-2026-48840

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading...

5.3 MediumFix available

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: Low
Integrity: None
Availability: None

Exploit likelihood

0.26%Up 0.2 points since May 30, 2026

What each source reports

CVE List Score used 5.3

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.

Record: CVE-2026-48840
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-839
Updated: 2026-11-02

EUVDEUVD-2026-33446 5.3

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.

Record: EUVD-2026-33446
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-wgrp-2w9f-fmvg 5.3

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading...

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.

Record: GHSA-wgrp-2w9f-fmvg
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-839
Updated: 2026-11-02

NVD 5.3

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.

Record: CVE-2026-48840
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-839
Updated: 2026-11-02

OSVALPINE-CVE-2026-48840 5.3

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.

Record: ALPINE-CVE-2026-48840
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-03

OSVDEBIAN-CVE-2026-48840 5.3

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.

Record: DEBIAN-CVE-2026-48840
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-02

OSVUBUNTU-CVE-2026-48840 5.3

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.

Record: UBUNTU-CVE-2026-48840
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-02

OSVUSN-8353-1 No score

exim4 vulnerability

Warisjeet Singh discovered that Exim with SUPPORT_PROXY enabled did not properly handle memory before SMTP authentication. A remote attacker could possibly use this issue to obtain sensitive information.

Record: USN-8353-1
Updated: 2026-11-02

OSVUSN-8382-1 No score

exim4 vulnerabilities

Timo Longin discovered that Exim incorrectly handled certain SMTP messages in PIPELINING/CHUNKING configurations. A remote attacker could possibly use this issue to perform SMTP smuggling. This issue only affected Ubuntu 14.04 LTS. (CVE-2023-51766)

It was discovered that Exim incorrectly handled certain malformed JSON data in headers. A remote attacker could possibly use this issue to crash Exim, resulting in a denial of service, or execute arbitrary code. This issue only affected Ubuntu 20.04 LTS. (CVE-2026-40685)

It was discovered that Exim incorrectly handled certain malformed UTF-8 headers. A remote attacker could possibly use this issue to obtain sensitive information. This issue only affected Ubuntu 20.04 LTS. (CVE-2026-40686)

It was discovered that Exim incorrectly handled certain SPA resources. A remote attacker could possibly use this issue to crash Exim, resulting in a denial of service, or obtain sensitive information. This issue only affected Ubuntu 20.04 LTS. (CVE-2026-40687)

It was discovered that Exim incorrectly handled certain CHUNKING transfers in some GnuTLS configurations. A remote attacker could possibly use this issue to crash Exim, resulting in a denial of service, or execute arbitrary code. This issue only affected Ubuntu 20.04 LTS. (CVE-2026-45185)

Warisjeet Singh discovered that Exim incorrectly handled certain proxy connections in builds with proxy support enabled. A remote attacker could possibly use this issue to obtain sensitive information. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2026-48840)

Record: USN-8382-1
Updated: 2026-11-02

Affected products

exim

Affected packages

Affected packages
Package	Affected	Fixed
`exim` Alpine:v3.23	4.88 up to 4.98.4-r0	4.98.4-r0
`exim` Alpine:v3.24	4.88 up to 4.98.4-r0	4.98.4-r0
`exim4` Debian:12	before 4.96-15+deb12u10, plus listed versions 4.96-154.96-15+deb12u14.96-15+deb12u24.96-15+deb12u34.96-15+deb12u4 Show 5 moreShow less 4.96-15+deb12u54.96-15+deb12u64.96-15+deb12u74.96-15+deb12u84.96-15+deb12u9	4.96-15+deb12u10
`exim4` Debian:13	before 4.98.2-1+deb13u3, plus listed versions 4.98.2-14.98.2-1+deb13u14.98.2-1+deb13u2	4.98.2-1+deb13u3
`exim4` Debian:14	before 4.99.3-2, plus listed versions 4.98.2-14.98.2-1+hurd.14.98.2-24.99-14.99-2 Show 25 moreShow less 4.99-34.99-44.99-4~bpo13+14.99-54.99-64.99-6~bpo13+14.99-74.99-7~bpo13+14.99.1-14.99.1-1~bpo13+14.99.1-24.99.1-34.99.1-44.99.1-54.99.1-64.99.2-14.99.2-1~bpo13+14.99.2-24.99.2-2~bpo13+14.99.3-14.99.3-2~bpo13+14.99~RC1-14.99~RC2-14.99~RC3-14.99~RC3-2	4.99.3-2
`exim4` Ubuntu:Pro:16.04:LTS	before 4.86.2-2ubuntu2.6+esm9, plus listed versions 4.86-3ubuntu14.86-7ubuntu14.86-7ubuntu24.86-7ubuntu34.86.2-2ubuntu1 Show 14 moreShow less 4.86.2-2ubuntu24.86.2-2ubuntu2.14.86.2-2ubuntu2.24.86.2-2ubuntu2.34.86.2-2ubuntu2.44.86.2-2ubuntu2.54.86.2-2ubuntu2.64.86.2-2ubuntu2.6+esm14.86.2-2ubuntu2.6+esm24.86.2-2ubuntu2.6+esm44.86.2-2ubuntu2.6+esm54.86.2-2ubuntu2.6+esm64.86.2-2ubuntu2.6+esm74.86.2-2ubuntu2.6+esm8	4.86.2-2ubuntu2.6+esm9
`exim4` Ubuntu:Pro:18.04:LTS	before 4.90.1-1ubuntu1.10+esm6, plus listed versions 4.89-5ubuntu14.89-9ubuntu14.89-9ubuntu24.89-9ubuntu34.89-9ubuntu4 Show 14 moreShow less 4.90.1-1ubuntu14.90.1-1ubuntu1.14.90.1-1ubuntu1.24.90.1-1ubuntu1.34.90.1-1ubuntu1.44.90.1-1ubuntu1.54.90.1-1ubuntu1.84.90.1-1ubuntu1.94.90.1-1ubuntu1.104.90.1-1ubuntu1.10+esm14.90.1-1ubuntu1.10+esm24.90.1-1ubuntu1.10+esm34.90.1-1ubuntu1.10+esm44.90.1-1ubuntu1.10+esm5	4.90.1-1ubuntu1.10+esm6
`exim4` Ubuntu:Pro:20.04:LTS	before 4.93-13ubuntu1.12+esm1, plus listed versions 4.92.1-1ubuntu34.92.1-1ubuntu44.93~RC2-1ubuntu14.93-9ubuntu14.93-11ubuntu1 Show 11 moreShow less 4.93-12ubuntu14.93-13ubuntu14.93-13ubuntu1.14.93-13ubuntu1.54.93-13ubuntu1.64.93-13ubuntu1.74.93-13ubuntu1.84.93-13ubuntu1.94.93-13ubuntu1.104.93-13ubuntu1.114.93-13ubuntu1.12	4.93-13ubuntu1.12+esm1
`exim4` Ubuntu:22.04:LTS	before 4.95-4ubuntu2.9, plus listed versions 4.94.2-7ubuntu24.95-2ubuntu24.95-4ubuntu14.95-4ubuntu24.95-4ubuntu2.1 Show 7 moreShow less 4.95-4ubuntu2.24.95-4ubuntu2.34.95-4ubuntu2.44.95-4ubuntu2.54.95-4ubuntu2.64.95-4ubuntu2.74.95-4ubuntu2.8	4.95-4ubuntu2.9
`exim4` Ubuntu:24.04:LTS	before 4.97-4ubuntu4.6, plus listed versions 4.96-17ubuntu24.96-17ubuntu2.14.97-3ubuntu14.97-4ubuntu14.97-4ubuntu3 Show 6 moreShow less 4.97-4ubuntu44.97-4ubuntu4.14.97-4ubuntu4.24.97-4ubuntu4.34.97-4ubuntu4.44.97-4ubuntu4.5	4.97-4ubuntu4.6
`exim4` Ubuntu:25.10	before 4.98.2-1ubuntu2.3, plus listed versions 4.98.1-1ubuntu24.98.2-1ubuntu14.98.2-1ubuntu24.98.2-1ubuntu2.14.98.2-1ubuntu2.2	4.98.2-1ubuntu2.3
`exim4` Ubuntu:26.04:LTS	before 4.99.1-1ubuntu1.3, plus listed versions 4.98.2-1ubuntu24.99-4ubuntu14.99.1-1ubuntu14.99.1-1ubuntu1.14.99.1-1ubuntu1.2	4.99.1-1ubuntu1.3
`exim4` Ubuntu:Pro:14.04:LTS	before 4.82-3ubuntu2.4+esm9, plus listed versions 4.80-7ubuntu34.80-7ubuntu44.80-9ubuntu14.80-9ubuntu24.82-3ubuntu1 Show 12 moreShow less 4.82-3ubuntu24.82-3ubuntu2.14.82-3ubuntu2.24.82-3ubuntu2.34.82-3ubuntu2.44.82-3ubuntu2.4+esm14.82-3ubuntu2.4+esm24.82-3ubuntu2.4+esm34.82-3ubuntu2.4+esm44.82-3ubuntu2.4+esm64.82-3ubuntu2.4+esm74.82-3ubuntu2.4+esm8	4.82-3ubuntu2.4+esm9

History

History
Recorded	Changed	Sources
Nov 3, 2026	affected, aliases, references	OSV
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-48840 is a medium vulnerability (CVSS 5.3) in Exim, published May 29, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.26%, the 18th percentile. Fixed in exim 4.98.4-r0.

References

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