Description
Exim 4 before 4.94.2 allows Use After Free in smtp_reset in certain situations that may be common for builds with OpenSSL.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | exim4 | 4.94.2-1 | — |
| Debian 13 | exim4 | 4.94.2-1 | — |
| Debian 12 | exim4 | 4.94.2-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | exim4 | 4.93-13ubuntu1.5 | USN-4934-1 |
| Ubuntu 18.04 LTS | exim4 | 4.90.1-1ubuntu1.8 | USN-4934-1 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SUSE Package Hub 15 SP2 | exim | 4.94.2-bp152.6.4.1 | openSUSE-SU-2021:0754-1 |
| SUSE Package Hub 15 SP2 | libspf2 | 1.2.10-bp152.5.1 | openSUSE-SU-2021:0754-1 |
| SUSE Package Hub 15 SP1 | exim | 4.94.2-bp151.2.4.1 | openSUSE-SU-2021:0753-1 |
| SUSE Package Hub 15 SP1 | libspf2 | 1.2.10-bp151.4.1 | openSUSE-SU-2021:0753-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | exim | 4.94.2-4.2 | openSUSE-SU-2024:10746-1 |
| openSUSE Leap 15.2 | exim | 4.94.2-lp152.8.3.1 | openSUSE-SU-2021:0677-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | exim | 4.94.2-r0 | — |
| Alpine v3.23 | exim | 4.94.2-r0 | — |
| Alpine v3.22 | exim | 4.94.2-r0 | — |
| Alpine v3.21 | exim | 4.94.2-r0 | — |
| Alpine v3.20 | exim | 4.94.2-r0 | — |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | exim | 4.94.2-r0 | — |
| Alpine v3.18 | exim | 4.94.2-r0 | — |
| Alpine v3.17 | exim | 4.94.2-r0 | — |
| Alpine v3.16 | exim | 4.94.2-r0 | — |
| Alpine v3.15 | exim | 4.94.2-r0 | — |
| Alpine v3.14 | exim | 4.94.2-r0 | — |
| Alpine v3.13 | exim | 4.94.2-r0 | — |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
GitHub 1 repository
-
dorkerdevil/CVE-2020-28018 ★ 7 · May 15, 2021
exim use after free exploit and detection
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 5
- USN-4934-1 exim4 vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- openSUSE-SU-2021:0754-1 Security update for exim SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:10746-1 exim-4.94.2-4.2 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:0677-1 Security update for exim SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:0753-1 Security update for exim SUSE / openSUSE Security Updates · Feb 4, 2026
References
- https://www.exim.org/static/doc/security/CVE-2020-qualys/CVE-2020-28018-OCORK.txt
- [oss-security] 20210511 [CVE-2020-28018] Use-After-Free on Exim Question mailing-list
- [oss-security] 20210511 Re: [CVE-2020-28018] Use-After-Free on Exim Question mailing-list
- [oss-security] 20210511 Re: [CVE-2020-28018] Use-After-Free on Exim Question mailing-list
- [oss-security] 20210511 Re: [CVE-2020-28018] Use-After-Free on Exim Question mailing-list
- [oss-security] 20210511 Re: [CVE-2020-28018] Use-After-Free on Exim Question mailing-list
- [oss-security] 20210512 Re: [CVE-2020-28018] Use-After-Free on Exim Question mailing-list
- [oss-security] 20210512 Re: [CVE-2020-28018] Use-After-Free on Exim Question mailing-list