From 937ac1fe069a4dc8471dff205f553d82e724015b Mon Sep 17 00:00:00 2001 From: Ned Deily Date: Sun, 11 Mar 2018 14:29:05 -0400 Subject: [PATCH] [3.5] bpo-32981: Fix catastrophic backtracking vulns (GH-5955) (#6034) * 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 Co-authored-by: Christian Heimes . (cherry picked from commit 0e6c8ee2358a2e23117501826c008842acb835ac) --- Lib/difflib.py | 2 +- Lib/poplib.py | 2 +- Lib/test/test_difflib.py | 22 ++++++++++++++++++- Lib/test/test_poplib.py | 12 +++++++++- Misc/ACKS | 1 + .../2018-03-02-10-24-52.bpo-32981.O_qDyj.rst | 4 ++++ 6 files changed, 39 insertions(+), 4 deletions(-) create mode 100644 Misc/NEWS.d/next/Security/2018-03-02-10-24-52.bpo-32981.O_qDyj.rst diff --git a/Misc/NEWS.d/next/Security/2018-03-02-10-24-52.bpo-32981.O_qDyj.rst b/Misc/NEWS.d/next/Security/2018-03-02-10-24-52.bpo-32981.O_qDyj.rst new file mode 100644 index 000000000000..9ebabb44f91e --- /dev/null +++ b/Misc/NEWS.d/next/Security/2018-03-02-10-24-52.bpo-32981.O_qDyj.rst @@ -0,0 +1,4 @@ +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.