Bug 1663908 (CVE-2018-20538)

Summary:	CVE-2018-20538 nasm: Use-after-free at asm/preproc.c resulting in a denial of service
Product:	[Other] Security Response	Reporter:	Andrej Nemec <anemec>
Component:	vulnerability	Assignee:	Nobody <nobody>
Status:	ASSIGNED ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	dominik, java-sig-commits, mizdebsk, nickc
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1663909, 1677017, 1677018
Bug Blocks:	1663910

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.