SPA authentication bypass in Exim

Published: 2020-05-18 | Updated: 2020-06-02
Risk Medium
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2020-12783
Exploitation vector Network
Public exploit N/A
Vulnerable software
Server applications / Mail servers

Vendor Exim

Security Bulletin

This security bulletin contains information about 1 vulnerabilities.

Updated: 02.06.2020

Changed bulletin status to patched.

1) Out-of-bounds read

EUVDB-ID: #VU27959

Risk: Medium

CVSSv3.1: 4.9 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:U/RL:U/RC:C]

CVE-ID: CVE-2020-12783

CWE-ID: CWE-125 - Out-of-bounds read

Exploit availability: No


The vulnerability allows a remote attacker to gain access to potentially sensitive information.

The vulnerability exists due to a boundary condition in the SPA authenticator within auths/spa.c and auths/auth-spa.c. A remote attacker can bypass SPA/NTLM authentication.


Install update from vendor's website.

Vulnerable software versions

Exim: 4.00 -

External links

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.