CVE-2017-16944 — The receive_msg function in receive

The receive_msg function in receive.c in the SMTP daemon in Exim 4.88 and 4.89 allows remote attackers to cause a denial of service (infinite loop and stack exhaustion) via vectors involving BDAT commands and an improper check for a '.' character signifying the end of t

01What is this vulnerability?

The receive_msg function in receive.c in the SMTP daemon in Exim 4.88 and 4.89 allows remote attackers to cause a denial of service (infinite loop and stack exhaustion) via vectors involving BDAT commands and an improper check for a '.' character signifying the end of the content, related to the bdat_getc function.

02Affected products

No structured affected-product list available — see references below for vendor advisories.

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2017-11-25T17:29:00.307
• Last modified: 2026-05-13T00:24:29.033

09References

• openwall.com — http://openwall.com/lists/oss-security/2017/11/25/1
• openwall.com — http://openwall.com/lists/oss-security/2017/11/25/2
• openwall.com — http://openwall.com/lists/oss-security/2017/11/25/3
• www.openwall.com — http://www.openwall.com/lists/oss-security/2021/05/04/7
• www.securitytracker.com — http://www.securitytracker.com/id/1039873
• bugs.exim.org — https://bugs.exim.org/show_bug.cgi?id=2201
• lists.exim.org — https://lists.exim.org/lurker/message/20171125.034842.d1d75cac.en.html
• www.debian.org — https://www.debian.org/security/2017/dsa-4053
• www.exploit-db.com — https://www.exploit-db.com/exploits/43184/
• openwall.com — http://openwall.com/lists/oss-security/2017/11/25/1