CVE-2020-28019
published 2021-05-06CVE-2020-28019: Exim 4 before 4.94.2 has Improper Initialization that can lead to recursion-based stack consumption or other consequences. This occurs because use of certain…
PriorityP358high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
61.06%
99.0th percentile
Exim 4 before 4.94.2 has Improper Initialization that can lead to recursion-based stack consumption or other consequences. This occurs because use of certain getc functions is mishandled when a client uses BDAT instead of DATA.
Affected
2 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | exim4 | < exim4 4.94.2-1 (bookworm) | exim4 4.94.2-1 (bookworm) |
| exim | exim | >= 4.88 < 4.94.2 | 4.94.2 |
Detection & IOCsextracted from sources · hover to see the quote
snort
alert smtp any any -> [$HOME_NET,$HTTP_SERVERS,$SMTP_SERVERS] any (msg:"ET EXPLOIT Exim Stack Exhaustion via BDAT Error Inbound (CVE-2020-28019)"; flow:established,to_server; content:"BDAT|20|"; pcre:"/^[^\r\n]{50,}/R"; content:"BDAT|20|"; distance:0; fast_pattern; reference:url,www.qualys.com/2021/05/04/21nails/21nails.txt; reference:cve,2020-28019; classtype:attempted-admin; sid:2032903; rev:1; metadata:attack_target SMTP_Server, created_at 2021_05_04, cve CVE_2020_28019, deployment Perimeter, deployment Internal, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_05_04;)- →Exploit traffic targets SMTP servers and uses the BDAT command (instead of DATA) with an oversized argument line (50+ non-CRLF characters). Detect by matching the literal bytes 'BDAT ' (BDAT|20|) on an established inbound SMTP connection.
- →The vulnerability is triggered when a client uses BDAT instead of DATA, causing mishandling of certain getc functions leading to recursion-based stack consumption. ↗
- ·Vulnerable versions are Exim 4 before 4.94.2. Fixed version is 4.94.2 (Debian packages: 4.94.2-1 across bookworm, bullseye, forky, sid, trixie). ↗
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvdv2.05.0MEDIUMAV:N/AC:L/Au:N/C:N/I:N/A:P
osv7.5HIGH
vendor_debian7.5HIGH
Stop checking back — get the weekly exploitation signal.
Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.
GHSA
GHSA-vxgq-8r56-c922: Exim 4 before 4
ghsa_unreviewed·2022-05-24
CVE-2020-28019 [HIGH] CWE-665 GHSA-vxgq-8r56-c922: Exim 4 before 4
Exim 4 before 4.94.2 has Improper Initialization that can lead to recursion-based stack consumption or other consequences. This occurs because use of certain getc functions is mishandled when a client uses BDAT instead of DATA.
OSV
CVE-2020-28019: Exim 4 before 4
osv·2021-05-06·CVSS 7.5
CVE-2020-28019 [HIGH] CVE-2020-28019: Exim 4 before 4
Exim 4 before 4.94.2 has Improper Initialization that can lead to recursion-based stack consumption or other consequences. This occurs because use of certain getc functions is mishandled when a client uses BDAT instead of DATA.
Ubuntu
Exim vulnerabilities
vendor_ubuntu·2021-05-04
CVE-2020-28022 Exim vulnerabilities
Title: Exim vulnerabilities
Summary: Several security issues were fixed in Exim.
It was discovered that Exim contained multiple security issues. An attacker
could use these issues to cause a denial of service, execute arbitrary
code remotely, obtain sensitive information, or escalate local privileges.
Instructions: In general, a standard system update will make all the necessary changes.
Debian
CVE-2020-28019: exim4 - Exim 4 before 4.94.2 has Improper Initialization that can lead to recursion-base...
vendor_debian·2020·CVSS 7.5
CVE-2020-28019 [HIGH] CVE-2020-28019: exim4 - Exim 4 before 4.94.2 has Improper Initialization that can lead to recursion-base...
Exim 4 before 4.94.2 has Improper Initialization that can lead to recursion-based stack consumption or other consequences. This occurs because use of certain getc functions is mishandled when a client uses BDAT instead of DATA.
Scope: local
bookworm: resolved (fixed in 4.94.2-1)
bullseye: resolved (fixed in 4.94.2-1)
forky: resolved (fixed in 4.94.2-1)
sid: resolved (fixed in 4.94.2-1)
trixie: resolved (fixed in 4.94.2-1)
Suricata
ET EXPLOIT Exim Stack Exhaustion via BDAT Error Inbound (CVE-2020-28019)
suricata·2021-05-04·CVSS 7.5
CVE-2020-28019 [HIGH] ET EXPLOIT Exim Stack Exhaustion via BDAT Error Inbound (CVE-2020-28019)
ET EXPLOIT Exim Stack Exhaustion via BDAT Error Inbound (CVE-2020-28019)
Rule: alert smtp any any -> [$HOME_NET,$HTTP_SERVERS,$SMTP_SERVERS] any (msg:"ET EXPLOIT Exim Stack Exhaustion via BDAT Error Inbound (CVE-2020-28019)"; flow:established,to_server; content:"BDAT|20|"; pcre:"/^[^\r\n]{50,}/R"; content:"BDAT|20|"; distance:0; fast_pattern; reference:url,www.qualys.com/2021/05/04/21nails/21nails.txt; reference:cve,2020-28019; classtype:attempted-admin; sid:2032903; rev:1; metadata:attack_target SMTP_Server, created_at 2021_05_04, cve CVE_2020_28019, deployment Perimeter, deployment Internal, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_05_04;)
No public exploits indexed.
2021-05-06
Published