CVE-2010-4344: Exim Heap-Based Buffer Overflow Vulnerability

Is it exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 25 Mar 2022, 4,119 days after the CVE record was published.

How likely is exploitation in the next 30 days?

71.7%

EPSS score, percentile 99.4 of all scored records

How severe?

9.8 Critical

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

Required action (CISA), due 15 Apr 2022: Apply updates per vendor instructions.

Advisories and patches (4)

Which versions are affected?

Not stated. The CVE record gives vendor and product as “n/a” and the version as “unspecified”.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

What to do

CISA due date for this action: 15 April 2022.

Advisories and patches

• SUSE-SA:2010:059 (Vendor advisory)
• RHSA-2010:0970 (Vendor advisory)
• USN-1032-1 (Vendor advisory)
• DSA-2131 (Vendor advisory)

Linked from CISA's catalog entry

• https://nvd.nist.gov/vuln/detail/CVE-2010-4344

Affected products and versions

The CVE record does not name affected products or versions: vendor and product are “n/a” and the version is “unspecified”.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

About this vulnerability

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.

Summary: CISA's KEV catalog, as of 28 Oct 2026.

• CISA added CVE-2010-4344 to its Known Exploited Vulnerabilities (KEV) catalog on 25 Mar 2022.
• CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
• The due date CISA sets for the required action is 15 Apr 2022.
• The CVE record was published on 14 Dec 2010, 4,119 days before it was added to KEV.
• The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), taken from CISA's enrichment of the record.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 71.7% (percentile 99.4), as of 28 Oct 2026.
• CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact total.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.

Description

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.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

Weakness

• CWE-787: Out-of-bounds Write
• CWE-119

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.

Timeline

References

• 42576 (Third-party advisory)
• 42587 (Third-party advisory)
• 40019 (Third-party advisory)
• VU#682457 (Third-party advisory)
• 42586 (Third-party advisory)
• 42589 (Third-party advisory)
• 1024858 (Vulnerability database)
• ADV-2010-3186 (Vulnerability database)

20 more in the CVE record.

More exploited Exim vulnerabilities

• CVE-2010-4345: Exim Privilege Escalation Vulnerability (added 25 Mar 2022)
• CVE-2019-16928: Exim Out-of-bounds Write Vulnerability (added 3 Mar 2022)
• CVE-2019-10149: Exim Mail Transfer Agent (MTA) Improper Input Validation (added 10 Jan 2022)
• CVE-2018-6789: Exim Buffer Overflow Vulnerability (added 3 Nov 2021)