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LIN9-10169 : Security Advisory - curl - CVE-2020-8177

Created: Jul 16, 2020    Updated: Jul 30, 2020
Resolved Date: Jul 30, 2020
Found In Version: 9.0.0.1
Severity: Standard
Applicable for: Wind River Linux 9
Component/s: Userspace

Description

curl can be tricked by a malicious server to overwrite a local file when using -J (--remote-header-name) and -i (--include) in the same command line.

The command line tool offers the -J option that saves a remote file using the file name present in the Content-Disposition: response header. curl then refuses to overwrite an existing local file using the same name, if one already exists in the current directory.

The -J flag is designed to save a response body, and so it doesn't work together with -i and there's logic that forbids it. However, the check is flawed and doesn't properly check for when the options are used in the reversed order: first using -J and then -i were mistakenly accepted.

The result of this mistake was that incoming HTTP headers could overwrite a local file if one existed, as the check to avoid the local file was done first when body data was received, and due to the mistake mentioned above, it could already have received and saved headers by that time.

The saved file would only get response headers added to it, as it would abort the saving when the first body byte arrives. A malicious server could however still be made to send back virtually anything as headers and curl would save them like this, until the first CRLF-CRLF sequence appears.

(Also note that -J needs to be used in combination with -O to have any effect.)

We are not aware of any exploit of this flaw.

CREATE(Triage):(User=admin) [CVE-2020-8177|https://nvd.nist.gov/vuln/detail/CVE-2020-8177]

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