A heap buffer overflow in BitmapScaleBitmaps in libXfont2 before 2.0.8 due to an overflowing 32bit size could be used by attackers able to access the X Server to execute code within the X server cont

A heap bufferflow in pcfReadFont() due to missing glyph bounds checking in libXfont2 before 2.0.8  allows attackers authenticated as X client to execute code within the X server.

A heap buffer overflow due to missing size checking in the property buffer when parsing PCF files in libXfont2 ComputeScaledProperties() before libXfont2 before 2.0.8 could be used by attackers using authenticated X clients to execute code within the X server.

In libXfont before 1.5.4 and libXfont2 before 2.0.3, a local attacker can open (but not read) files on the system as root, triggering tape rewinds, watchdogs, or similar mechanisms that can be triggered by opening files.

Stack-based buffer overflow in the bdfReadCharacters function in bitmap/bdfread.c in X.Org libXfont 1.1 through 1.4.6 allows remote attackers to cause a denial of service (crash) or possibly execute arbitrary code via a long string in a character name in a BDF font file.

Multiple buffer overflows in X.Org libXfont before 1.4.8 and 1.4.9x before 1.4.99.901 allow remote font servers to execute arbitrary code via a crafted xfs protocol reply to the (1) fsrecvconnsetup, (2) fsreadopenfont, (3) fsreadqueryinfo, (4) fsreadextentinfo, (5) fsreadglyphs, (6) fsreadlist, or (7) fsreadlistinfo function.

Multiple integer overflows in the (1) FontFileAddEntry and (2) lexAlias functions in X.Org libXfont before 1.4.8 and 1.4.9x before 1.4.99.901 might allow local users to gain privileges by adding a directory with a large fonts.dir or fonts.alias file to the font path, which triggers a heap-based buffer overflow, related to metadata.

Multiple integer overflows in the (1) fsgetreply, (2) fsallocglyphs, and (3) fsreadextentinfo functions in X.Org libXfont before 1.4.8 and 1.4.9x before 1.4.99.901 allow remote font servers to execute arbitrary code via a crafted xfs reply, which triggers a buffer overflow.

A memory corruption flaw was discovered in Xorg X server's Render extension. Problem originally reported as Firefox crashing X server issue was tracked down to an incorrect calculation issue in mod() macro by Olivier Fourdan:

https://bugzilla.redhat.com/showbug.cgi?id=495733#c15

This issue could cause mod() to return value greater than its second argument (the divisor), resulting in excessive read and write in Render composite operation, causing heap or video memory corruption.

XcursorThemeInherits in library.c in libXcursor before 1.1.15 allows remote attackers to cause denial of service or potentially code execution via a one-byte heap overflow.

A single byte overflow in catalogue.c in X.Org libXfont 1.3.1 allows remote attackers to have unspecified impact.

Integer overflow in the AllocateGlyph function in the Render extension in the X server 1.4 in X.Org X11R7.3 allows context-dependent attackers to execute arbitrary code via unspecified request fields that are used to calculate a heap buffer size, which triggers a heap-based buffer overflow.

Multiple integer overflows in the Render extension in the X server 1.4 in X.Org X11R7.3 allow context-dependent attackers to execute arbitrary code via a (1) SProcRenderCreateLinearGradient, (2) SProcRenderCreateRadialGradient, or (3) SProcRenderCreateConicalGradient request with an invalid field specifying the number of bytes to swap in the request data, which triggers heap memory corruption.

The (1) SProcRecordCreateContext and (2) SProcRecordRegisterClients functions in the Record extension and the (3) SProcSecurityGenerateAuthorization function in the Security extension in the X server 1.4 in X.Org X11R7.3 allow context-dependent attackers to execute arbitrary code via requests with crafted length values that specify an arbitrary number of bytes to be swapped on the heap, which triggers heap corruption.

Integer overflow in the fbShmPutImage function in the MIT-SHM extension in the X server 1.4 in X.Org X11R7.3 allows context-dependent attackers to read arbitrary process memory via crafted values for a Pixmap width and height.

The ProcRenderAddGlyphs function in the Render extension (render/render.c) in X.Org xserver 1.7.7 and earlier allows local users to read arbitrary memory and possibly cause a denial of service (server crash) via unspecified vectors related to an "input sanitization flaw."

BSD compress implemented an LZW compressor and decompressor. This decompressor implementation did not correctly handle compressed streams that contain code words that were not yet added to the decompression table. LZW decompression has a special case (a KwKwK string) when code word may match the first free entry in the decompression table. The implementation used in BSD compress allow code words not only matching, but also exceeding the first free entry.

It seems this compress implementation first appeared in BSD around 1985, and was later used in various other code base, such as ncompress and gzip. Other components that contain affected code will be listed below. Following page list the version of the code as was used in 4.3BSD:

http://minnie.tuhs.org/cgi-bin/utree.pl?file=4.3BSD-Reno/src/usr.bin/compress/compress.c

Relevant code appears in the decompress() routine:

/ Special case for KwKwK string. / if ( code >= freeent ) { stackp++ = finchar; code = oldcode; }

This allows creating a loop in the decompression table, which leads to an "infinite" loop:

/ Generate output characters in reverse order / #ifdef SIGNEDCOMPARESLOW while ( ((unsigned long)code) >= ((unsigned long)256) ) { #else while ( code >= 256 ) { #endif stackp++ = tabsuffixof(code); code = tabprefixof(code); }

where tabprefixof is:

unsigned short codetab [HSIZE]; #define codetabof(i) codetab[i] #define tabprefixof(i) codetabof(i)

This overflows destack "buffer" (part of the htab[]):

countint htab [HSIZE]; # define tabsuffixof(i) ((chartype )(htab))[i] # define destack ((chartype )&tabsuffixof(1<<BITS))

Depending on the relative htab[] and codetab[] positions, destack overflow may overwrite codetab[] entries, which may break infinite loop and let program continue its execution with possibly corrupted memory.

It was found that xrdb, the X server resource database utility, did not properly sanitize system host names, containing shell escape characters, during launch of user graphical session (when the display manager retrieved the system host name from resource database via xrdb). When the display manager was configured to listen for X Display Manager Control Protocol (XDMCP) messages, a remote attacker could use this flaw to remotely execute arbitrary code with the privileges, of the user running the display manager (usually privileged system user, root). On systems, where the XDMCP messages were disabled and the system was configured to retrieve its host name from remote DHCP server, a rogue DHCP server could use this flaw to possibly execute arbitrary code with the privileges of the user running the display manager (usually root) via a specially-crafted host name assigned to the victim host in question.

Note: ===== The display managers, shipped with Red Hat Enterprise Linux 4, 5, and 6 do not listen for remote XDMCP messages in the default configuration, which mitigates this security flaw to be exploitable only by rogue remote DHCP servers.

The display managers, shipped with Fedora release of 13 and 14 do not listen for remote XDMCP messages in the default configuration, which mitigates this security flaw to be exploitable only by rogue remote DHCP servers.

From the upstream announcement [1]:

A vulnerability has been found in the X11R6 font server code in the handling of the SetEventMask request in xfs - if an invalid mask is specified, it passes that bad mask to the SendErrToClient() function for returning to the client in the error message. Unfortunately, SendErrToClient() expects a pointer, but was being passed the raw mask value, causing it to use the mask as a pointer, either segfaulting (if that happened to be an invalid pointer), or returning whatever data happened to be accessible in the 4 bytes at the address specified by the mask value.

X11R6 through X11R6.6 appear to be vulnerable. The fix shown below was introduced by XFree86 in their 3.3.3 release as part of the commit for: Prototype/ansification cleanup for Xserver/XIE, xfs, fontlib, mkfontdir, and fix some bugs found along the way (#2103, Thomas Dickey).

X11R6.7 incorporated the XFree86 changes, and thus X11R6.7 and later releases from X.Org are not vulnerable.

[1] http://lists.freedesktop.org/archives/xorg-announce/2012-July/002040.html

Statement:

Not vulnerable. This issue did not affect the versions of xorg-x11-xfs as shipped with Red Hat Enterprise Linux 5. It does not affect Red Hat Enterprise Linux 6 as it no longer uses or provides the XFS font server.

It was found that XKB actions for debugging X.org clients were enabled by default. This could cause a screen locking application such as gnome-screensaver to be killed when those key combinations were triggered.

The debugging key actions were introduced in the following commit: http://cgit.freedesktop.org/xorg/xserver/commit/?id=7d2543a3cb3089241982ce4f8984fd723d5312a1

Reference: http://thread.gmane.org/gmane.comp.security.oss.general/6725

Mitigation: http://thread.gmane.org/gmane.comp.security.oss.general/6725/focus=6731

Use-after-free vulnerability in the doImageText function in dix/dixfonts.c in the xorg-server module before 1.14.4 in X.Org X11 allows remote authenticated users to cause a denial of service (daemon crash) or possibly execute arbitrary code via a crafted ImageText request that triggers memory-allocation failure.

X.Org xdm 1.1.10, 1.1.11, and possibly other versions, when performing authentication using certain implementations of the crypt API function that can return NULL, allows remote attackers to cause a denial of service (NULL pointer dereference and crash) by attempting to log into an account whose password field contains invalid characters, as demonstrated using the crypt function from glibc 2.17 and later with (1) the "!" character in the salt portion of a password field or (2) a password that has been encrypted using DES or MD5 in FIPS-140 mode.

Buffer overflow in X.org libXv 1.0.7 and earlier allows X servers to cause a denial of service (crash) and possibly execute arbitrary code via crafted length or index values to the XvQueryPortAttributes function.

X.Org X server before 1.13.4 and 1.4.x before 1.14.1 does not properly restrict access to input events when adding a new hot-plug device, which might allow physically proximate attackers to obtain sensitive information, as demonstrated by reading passwords from a tty.

Integer overflow in X.org libXcursor 1.1.13 and earlier allows X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the XcursorFileHeaderCreate function.

Buffer overflow in X.org libXvMC 1.0.7 and earlier allows X servers to cause a denial of service (crash) and possibly execute arbitrary code via crafted length or index values to the XvMCGetDRInfo function.

Integer overflow in X.org libxcb 1.9 and earlier allows X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the readpacket function.

Multiple integer overflows in X.org libXxf86dga 1.1.3 and earlier allow X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the (1) XDGAQueryModes and (2) XDGASetMode functions.

Integer overflow in X.org libXfixes 5.0 and earlier allows X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the XFixesGetCursorImage function.