CVE-2010-4344
CVE-2010-4344 is a security flaw in Exim, mail server software. Attackers can run their own code on Exim. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 25 Mar 2022.[1]
Exim is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff.
Description
CISA calls it a heap-based buffer overflow in Exim Exim. In its words: “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.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is memory buffer error (CWE-119), in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it. CISA names the product as Exim Exim.
Most families won’t have Exim; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 25 Mar 2022, 4,119 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 15 Apr 2022 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 72%. That’s in the top 1% of the flaws it scores.[3]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.Exim is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 15 Apr 2022 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 72%.[3] |
See also
Other Exim flaws
- CVE-2010-4345: privilege escalation ·
- CVE-2018-6789: buffer overflow ·
Other Exim flaws
- CVE-2019-16928, Exim Internet Mailer: out-of-bounds write ·
- CVE-2019-10149, Exim Mail Transfer Agent (MTA): improper input validation ·
Other memory buffer error flaws
- CVE-2026-88779, Citrix NetScaler: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88772, Citrix NetScaler: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88771, Citrix NetScaler: improper input validation ·
- CVE-2026-8452, Citrix NetScaler ADC and NetScaler Gateway: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2009-3459, Adobe Acrobat and Reader: heap-based buffer overflow ·
Added the same day
- CVE-2022-26318, WatchGuard Firebox and XTM Appliances: arbitrary code execution ·
- CVE-2022-26143, Mitel MiCollab, MiVoice Business Express: access control ·
- CVE-2022-21999, Microsoft Windows: print spooler privilege escalation ·
- CVE-2021-42237, Sitecore XP: remote command execution ·
- CVE-2021-22941, Citrix ShareFile: improper access control ·
Every Exim flaw on CISA’s list · Everything added in March 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “Exim Heap-Based Buffer Overflow Vulnerability”. Known Exploited Vulnerabilities Catalog, added 25 Mar 2022.
- ^ National Institute of Standards and Technology. “CVE-2010-4344 Detail”. National Vulnerability Database, published 14 Dec 2010.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.717, percentile 99.4, 31 Oct 2026.
- CVE Program. “CVE-2010-4344”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.