Bug 1663907 (CVE-2018-20535)

Summary:	CVE-2018-20535 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
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1663909, 1671502, 1671503
Bug Blocks:	1663910

Description Andrej Nemec 2019-01-07 09:53:43 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=3392530

Comment 1 Andrej Nemec 2019-01-07 09:54:59 UTC

Created nasm tracking bugs for this issue:

Affects: fedora-all [bug 1663909]

Comment 2 Nick Clifton 2019-01-17 10:37:38 UTC

Setting devel cond NAK - waiting on upstream fix.

Comment 3 Scott Gayou 2019-01-31 18:18:33 UTC

Red Hat Enterprise 6 and 7 are vulnerable. Valgrind output matches upstream's ASAN output relatively well:

```
poc:15: error: label or instruction expected at start of line
poc:16: error: attempt to define a local label before any non-local labels
poc:18: error: parser: instruction expected
poc:18: error: parser: instruction expected
poc:18: error: label or instruction expected at start of line
==12504== Invalid read of size 4
==12504==    at 0x4346C5: pp_getline (preproc.c:4957)
==12504==    by 0x4046E3: assemble_file.constprop.3 (nasm.c:1222)
==12504==    by 0x402D02: main (nasm.c:463)
```