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[2.7] bpo-32981: Fix catastrophic backtracking vulns (GH-5955)
* Prevent low-grade poplib REDOS (CVE-2018-1060) The regex to test a mail server's timestamp is susceptible to catastrophic backtracking on long evil responses from the server. Happily, the maximum length of malicious inputs is 2K thanks to a limit introduced in the fix for CVE-2013-1752. A 2KB evil response from the mail server would result in small slowdowns (milliseconds vs. microseconds) accumulated over many apop calls. This is a potential DOS vector via accumulated slowdowns. Replace it with a similar non-vulnerable regex. The new regex is RFC compliant. The old regex was non-compliant in edge cases. * Prevent difflib REDOS (CVE-2018-1061) The default regex for IS_LINE_JUNK is susceptible to catastrophic backtracking. This is a potential DOS vector. Replace it with an equivalent non-vulnerable regex. Also introduce unit and REDOS tests for difflib. Co-authored-by: Tim Peters <firstname.lastname@example.org> Co-authored-by: Christian Heimes <email@example.com>. (cherry picked from commit 0e6c8ee)
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|Regexes in difflib and poplib were vulnerable to catastrophic backtracking.|
|These regexes formed potential DOS vectors (REDOS). They have been|
|refactored. This resolves CVE-2018-1060 and CVE-2018-1061.|
|Patch by Jamie Davis.|