Bug 1663908 (CVE-2018-20538) - CVE-2018-20538 nasm: Use-after-free at asm/preproc.c resulting in a denial of service
Summary: CVE-2018-20538 nasm: Use-after-free at asm/preproc.c resulting in a denial of...
Status: ASSIGNED
Alias: CVE-2018-20538
Product: Security Response
Classification: Other
Component: vulnerability   
(Show other bugs)
Version: unspecified
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard: impact=low,public=20181118,reported=2...
Keywords: Security
Depends On: 1663909 1677017 1677018
Blocks: 1663910
TreeView+ depends on / blocked
 
Reported: 2019-01-07 09:54 UTC by Andrej Nemec
Modified: 2019-02-13 19:13 UTC (History)
4 users (show)

Fixed In Version:
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RHEL 7.3 requirements from Atomic Host:
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Description Andrej Nemec 2019-01-07 09:54:28 UTC
A use-after-free vulnerability was found in nasm. A specially crafted file could cause the application to crash.

Upstream issue:

https://bugzilla.nasm.us/show_bug.cgi?id=3392531

Comment 1 Andrej Nemec 2019-01-07 09:55:02 UTC
Created nasm tracking bugs for this issue:

Affects: fedora-all [bug 1663909]

Comment 2 Nick Clifton 2019-01-17 10:38:24 UTC
Setting devel cond NAK - waiting on upstream fix.

Comment 3 Scott Gayou 2019-02-13 18:58:34 UTC
Similar valgrind output as compared to ASAN:

```
==12467== Memcheck, a memory error detector
==12467== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==12467== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==12467== Command: nasm -f bin attachment.cgi?id=411689 -o xxx
==12467== 
==12467== Conditional jump or move depends on uninitialised value(s)
==12467==    at 0x42FD4E: tokenize (preproc.c:1006)
==12467==    by 0x434189: pp_getline (preproc.c:4969)
==12467==    by 0x4046E3: assemble_file.constprop.3 (nasm.c:1222)
==12467==    by 0x402D02: main (nasm.c:463)
==12467== 
==12467== Conditional jump or move depends on uninitialised value(s)
==12467==    at 0x42FBA1: tokenize (preproc.c:900)
==12467==    by 0x434189: pp_getline (preproc.c:4969)
==12467==    by 0x4046E3: assemble_file.constprop.3 (nasm.c:1222)
==12467==    by 0x402D02: main (nasm.c:463)
==12467== 
attachment.cgi?id=411689:15: error: label or instruction expected at start of line
attachment.cgi?id=411689:16: error: attempt to define a local label before any non-local labels
attachment.cgi?id=411689:18: error: parser: instruction expected
attachment.cgi?id=411689:18: error: parser: instruction expected
attachment.cgi?id=411689:18: error: label or instruction expected at start of line
==12467== Invalid read of size 4
==12467==    at 0x4346C5: pp_getline (preproc.c:4957)
==12467==    by 0x4046E3: assemble_file.constprop.3 (nasm.c:1222)
==12467==    by 0x402D02: main (nasm.c:463)
```

Looks valid.


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