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heap overflow wikipedia jump to content main menu main menu move to sidebar hide navigation main page contents current events random article about wikipedia contact us contribute help learn to edit community portal recent changes upload file special pages search search appearance donate create account log in personal tools donate create account log in contents move to sidebar hide top 1 consequences 2 detection and prevention 3 see also 4 references 5 external links toggle the table of contents heap overflow 11 languages čeština deutsch español فارسی français italiano 한국어 lombard polski português українська edit links article talk english read edit view history tools tools move to sidebar hide actions read edit view history general what links here related changes upload file permanent link page information cite this page get shortened url switch to legacy parser print export download as pdf printable version in other projects wikidata item appearance move to sidebar hide from wikipedia the free encyclopedia software anomaly a heap overflow heap overrun or heap smashing is a type of buffer overflow that occurs in the heap data area heap overflows are exploitable in a different manner to that of stack based overflows memory on the heap is dynamically allocated at runtime and typically contains program data exploitation is performed by corrupting this data in specific ways to cause the application to overwrite internal structures such as linked list pointers the canonical heap overflow technique overwrites dynamic memory allocation linkage such as malloc metadata and uses the resulting pointer exchange to overwrite a program function pointer for example on older versions of linux two buffers allocated next to each other on the heap could result in the first buffer overwriting the second buffer s metadata by setting the in use bit to zero of the second buffer and setting the length to a small negative value which allows null bytes to be copied when the program calls free on the first buffer it will attempt to merge these two buffers into a single buffer when this happens the buffer that is assumed to be freed will be expected to hold two pointers fd and bk in the first 8 bytes of the formerly allocated buffer bk gets written into fd and can be used to overwrite a pointer citation needed consequences edit an accidental overflow may result in data corruption or unexpected behavior by any process that accesses the affected memory area on operating systems without memory protection this could be any process on the system for example a microsoft jpeg gdi buffer overflow vulnerability could allow remote execution of code on the affected machine 1 ios jailbreaking often uses heap overflows to gain arbitrary code execution detection and prevention edit as with buffer overflows there are primarily three ways to protect against heap overflows several modern operating systems such as windows and linux provide some implementation of all three prevent execution of the payload by separating the code and data typically with hardware features such as nx bit introduce randomization so the heap is not found at a fixed offset typically with kernel features such as aslr address space layout randomization introduce sanity checks into the heap manager since version 2 3 6 the gnu libc includes protections that can detect heap overflows after the fact for example by checking pointer consistency when calling unlink however those protections against prior exploits were almost immediately shown to also be exploitable 2 3 in addition linux has included support for aslr since 2005 although pax introduced a better implementation years before also linux has included support for nx bit since 2004 microsoft has included protections against heap resident buffer overflows since april 2003 in windows server 2003 and august 2004 in windows xp with service pack 2 these mitigations were safe unlinking and heap entry header cookies later versions of windows such as vista server 2008 and windows 7 include removal of commonly targeted data structures heap entry metadata randomization expanded role of heap header cookie randomized heap base address function pointer encoding termination of heap corruption and algorithm variation normal data execution prevention dep and aslr also help to mitigate this attack 4 the most common detection method for heap overflows is online dynamic analysis this method observes the runtime execution of programs to identify vulnerabilities through the detection of security breaches 5 see also edit buffer overflow heap spraying stack buffer overflow exploit shellcode references edit microsoft security bulletin ms04 028 buffer overrun in jpeg processing gdi could allow code execution 833987 microsoft 14 sep 2004 retrieved 29 mar 2016 the malloc maleficarum oct 2005 retrieved 24 april 2017 malloc des maleficarum 2009 retrieved 29 mar 2016 preventing the exploitation of user mode heap corruption vulnerabilities technet blog microsoft security research defense 4 aug 2009 retrieved 29 mar 2016 usenix association ed 2005 proceedings of the second workshop on real large distributed systems december 13 2005 san francisco ca usa usenix association isbn 978 1 931971 40 9 external links edit vudo malloc tricks heap overflow article at heise security defeating microsoft windows xp sp2 heap protection and dep bypass archived 2013 11 01 at the wayback machine retrieved from https en wikipedia org w index php title heap_overflow oldid 1359249620 categories computer security exploits software anomalies hidden categories articles with short description short description is different from wikidata all articles with unsourced statements articles with unsourced statements from june 2026 webarchive template wayback links this page was last edited on 14 june 2026 at 03 07 utc page was rendered with parsoid text is available under the creative commons attribution sharealike 4 0 license additional terms may apply by using this site you agree to the terms of use and privacy policy wikipedia is a registered trademark of the wikimedia foundation inc a non profit organization privacy policy about wikipedia disclaimers contact wikipedia legal safety contacts code of conduct developers statistics cookie statement mobile view search search toggle the table of contents heap overflow 11 languages add topic