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CVE-2017-16943

56
FAUCET Score

CVE-2017-16943 is a critical use-after-free vulnerability in the Exim SMTP daemon, specifically affecting versions 4.88 and 4.89, including those in Debian Linux. This flaw allows remote, unauthenticated attackers to execute arbitrary code or cause a denial of service through specially crafted BDAT commands. With a CVSS score of 9.8 and an EPSS score indicating high exploitability, the impact is severe, leading to complete compromise of confidentiality, integrity, and availability. While no public exploit code is readily available in common frameworks like Metasploit or ExploitDB, the vulnerability garnered significant media attention and community discussion, highlighting its potential for widespread impact on internet email servers.

Impacted Technologies

VendorProductVersion(s)CPE
4.88CPE matchmatch criteria
cpe:2.3:a:exim:exim:4.88:-:*:*:*:*:*:*
4.89CPE matchmatch criteria
cpe:2.3:a:exim:exim:4.89:-:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

9.8CRITICAL

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
46.71%
Probability of exploitation in next 30 days
EPSS Percentile
98.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.4671 is in the 96th percentile among its peer group of 36,833 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

redhatCVE-2017-16943Critical

exim: use-after-free in receive_msg function via vectors involving BDAT commands

Nov 23, 2017

References

openwall.com / lists/oss-security/2017/11/25/1
Mailing List
openwall.com / lists/oss-security/2017/11/25/2
Mailing List
openwall.com / lists/oss-security/2017/11/25/3
Mailing List
bugs.exim.org / show_bug.cgi
ExploitIssue Tracking
git.exim.org / exim.git/commit/4090d62a4b25782129cc1643596dc2f6e8f63bde
Patch
git.exim.org / exim.git/commitdiff/4e6ae6235c68de243b1c2419027472d7659aa2b4
Patch
github.com / LetUsFsck/PoC-Exploit-Mirror/tree/master/CVE-2017-16944
Exploit
lists.exim.org / lurker/message/20171125.034842.d1d75cac.en.html
Mailing List
debian.org / security/2017/dsa-4053
Third Party Advisory
openwall.com / lists/oss-security/2021/05/04/7
securitytracker.com / id/1039872
Third Party AdvisoryVDB Entry