CVE-2019-11841 Information

Description

A message-forgery issue was discovered in crypto/openpgp/clearsign/clearsign.go in supplementary Go cryptography libraries 2019-03-25. According to the OpenPGP Message Format specification in RFC 4880 chapter 7 a cleartext signed message can contain one or more optional \Hash\ Armor Headers. The \Hash\ Armor Header specifies the message digest algorithm(s) used for the signature. However the Go clearsign package ignores the value of this header which allows an attacker to spoof it. Consequently an attacker can lead a victim to believe the signature was generated using a different message digest algorithm than what was actually used. Moreover since the library skips Armor Header parsing in general an attacker can not only embed arbitrary Armor Headers but also prepend arbitrary text to cleartext messages without invalidating the signatures.

CVSS Vector

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Reference

http://packetstormsecurity.com/files/152840/Go-Cryptography-Libraries-Cleartext-Message-Spoofing.html https://go.googlesource.com/crypto/ https://lists.debian.org/debian-lts-announce/2019/09/msg00011.html https://lists.debian.org/debian-lts-announce/2020/10/msg00014.html https://sec-consult.com/ https://sec-consult.com/en/blog/advisories/cleartext-message-spoofing-in-go-cryptography-libraries-cve-2019-11841/

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

HIGH

Base Score

NONE

Base Severity

5.9