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Bug 1547779 - (CVE-2018-6798) CVE-2018-6798 perl: heap read overflow in regexec.c
CVE-2018-6798 perl: heap read overflow in regexec.c
Status: NEW
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
medium Severity medium
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Assigned To: Red Hat Product Security
impact=moderate,public=20180414,repor...
: Security
Depends On: 1567796 1561100 1561101 1561102 1567777
Blocks: 1547784
  Show dependency tree / graph
 
Reported: 2018-02-21 17:49 EST by Laura Pardo
Modified: 2018-04-23 02:50 EDT (History)
18 users (show)

See Also:
Fixed In Version: perl 5.26.2, perl 5.24.4
Doc Type: If docs needed, set a value
Doc Text:
A heap buffer over read flaw was found in the way Perl regular expression engine handled inputs with invalid UTF-8 characters. An attacker able to provide a specially crafted input to be matched against a regular expression could cause Perl interpreter to crash or disclose portion of its memory.
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External Trackers
Tracker ID Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2018:1192 None None None 2018-04-23 02:50 EDT

  None (edit)
Description Laura Pardo 2018-02-21 17:49:34 EST 
A flaw was found in Perl 5. A heap read overflow in regexec.c file may allow an attacker to cause a segmentation fault which might lead to a Denial of Service (DoS) or, possibly, heap memory disclosure.

Matching a crafted locale dependent regular expression can cause a heap buffer read overflow and potentially information disclosure while reporting an error message. That error message includes bytes beyond the end of the string, and possibly beyond the end of the buffer, providing a potential information disclosure if the memory had contained any sensitive information.
Comment 1 Petr Pisar 2018-02-22 08:33:36 EST 
Reproducer:

$ valgrind -- perl -e '"\xff" =~ /(?il)\x{100}|\x{100}/;' 
==18228== Memcheck, a memory error detector
==18228== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==18228== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==18228== Command: perl -e "\\xff"\ =~\ /(?il)\\x{100}|\\x{100}/;
==18228== 
==18228== Invalid read of size 1
==18228==    at 0x499C4E5: Perl__byte_dump_string (in /usr/lib/libperl.so.5.26.1)
==18228==    by 0x499CF02: Perl_utf8n_to_uvchr_error (in /usr/lib/libperl.so.5.26.1)
==18228==    by 0x499D88D: Perl__force_out_malformed_utf8_message (in /usr/lib/libperl.so.5.26.1)
==18228==    by 0x49A23CB: Perl__to_utf8_fold_flags (in /usr/lib/libperl.so.5.26.1)
==18228==    by 0x4995499: ??? (in /usr/lib/libperl.so.5.26.1)
==18228==    by 0x499A4AF: Perl_regexec_flags (in /usr/lib/libperl.so.5.26.1)
[...]
Comment 11 Cedric Buissart 2018-04-16 04:06:28 EDT 
Created perl tracking bugs for this issue:

Affects: fedora-all [bug 1567777]
Comment 13 Cedric Buissart 2018-04-16 05:43:33 EDT 
Statement:

Versions of the perl interpreter older than 5.22 are not vulnerable. As a result, the versions of perl as shipped in Red Hat Enterprise Linux version 7, 6 and 5, as well as the versions of  rh-perl520-perl as shipped with Red Hat Software Collections are not affected by this vulnerability.
Comment 14 Cedric Buissart 2018-04-16 05:43:43 EDT 
External References:

https://rt.perl.org/Public/Bug/Display.html?id=132063
Comment 18 Cedric Buissart 2018-04-18 10:31:59 EDT 
Acknowledgments:

Name: Perl 5 Porters
Upstream: Nguyen Duc Manh
Comment 19 errata-xmlrpc 2018-04-23 02:50:26 EDT 
This issue has been addressed in the following products:

  Red Hat Software Collections for Red Hat Enterprise Linux 6
  Red Hat Software Collections for Red Hat Enterprise Linux 6.7 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7
  Red Hat Software Collections for Red Hat Enterprise Linux 7.3 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7.4 EUS

Via RHSA-2018:1192 https://access.redhat.com/errata/RHSA-2018:1192
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