#VU27959 Out-of-bounds read in Exim - CVE-2020-12783

Vulnerability identifier: #VU27959

Vulnerability risk: Medium

CVSSv4.0: 2.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2020-12783

CWE-ID: CWE-125

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Exim
Server applications / Mail servers

Vendor: Exim

Description

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.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Exim: 4.00 - 4.93.0.4

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External links
https://bugs.exim.org/show_bug.cgi?id=2571
https://git.exim.org/exim.git/commit/57aa14b216432be381b6295c312065b2fd034f86
https://git.exim.org/exim.git/commit/a04174dc2a84ae1008c23b6a7109e7fa3fb7b8b0
https://www.debian.org/security/2020/dsa-4687

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Q & A

Can this vulnerability be exploited remotely?

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

Is there known malware, which exploits this vulnerability?

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