What is CVE-2010-4344?

CVE-2010-4344 is a critical-severity vulnerability in Exim, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2010-12-14.

How severe is CVE-2010-4344?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2010-4344 known to be exploited?

Yes. CVE-2010-4344 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-25), indicating it is being actively exploited. 10 public proof-of-concept repositories are indexed.

Buffer overflow in Exim

CVE-2010-4344

Heap-based buffer overflow in the string_vformat function in string.c in Exim before 4.70 allows remote attackers to execute arbitrary code via an SMTP session that includes two MAIL commands in conjunction with a large message containing crafted headers, leading to improper rejection logging.

Vulnerability class: Buffer Overflow

Published 2010-12-14 · last modified 2026-06-16.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.717 (99.4th percentile), scored 2026-10-17.

High probability of exploitation in the next 30 days — patch promptly. 99th percentile — 99.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.717 · newest: 0.717 · change: 0.000

Affected products

Exim
Canonical Ubuntu Linux — versions 6.06, 8.04, 9.10
Debian Linux — versions 5.0
openSUSE — versions 11.1, 11.2, 11.3

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2022-03-25. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2022-04-15.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

lists.opensuse.org/opensuse-security-announce/2010-12/msg00003.html (vendor-advisory, Mailing List, Third Party Advisory)
www.exim.org/lurker/message/20101207.215955.bb32d4f2.en.html (mailing-list, Exploit, Mailing List)
bugs.exim.org/show_bug.cgi (Patch, Issue Tracking)
www.securitytracker.com/id (VDB Entry, Third Party Advisory, vdb-entry, Broken Link)
www.redhat.com/support/errata/RHSA-2010-0970.html (vendor-advisory, Broken Link)
www.vupen.com/english/advisories/2010/3186 (vdb-entry, Broken Link, Vendor Advisory)
www.securityfocus.com/bid/45308 (VDB Entry, Third Party Advisory, vdb-entry, Broken Link)
www.metasploit.com/modules/exploit/unix/smtp/exim4_string_format (Third Party Advisory)
atmail.com/blog/2010/atmail-6204-now-available/ (Broken Link)
secunia.com/advisories/42576 (Broken Link, Vendor Advisory, third-party-advisory)

Frequently asked questions

What is CVE-2010-4344?: CVE-2010-4344 is a critical-severity vulnerability in Exim, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2010-12-14.
How severe is CVE-2010-4344?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2010-4344 known to be exploited?: Yes. CVE-2010-4344 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-25), indicating it is being actively exploited. 10 public proof-of-concept repositories are indexed.