CWE-786 Detail

CWE-786

Access of Memory Location Before Start of Buffer
Incomplete
2009-10-29
00h00 +00:00
2024-07-16
00h00 +00:00
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Name: Access of Memory Location Before Start of Buffer

The product reads or writes to a buffer using an index or pointer that references a memory location prior to the beginning of the buffer.

CWE Description

This typically occurs when a pointer or its index is decremented to a position before the buffer, when pointer arithmetic results in a position before the beginning of the valid memory location, or when a negative index is used.

General Informations

Common Consequences

Scope Impact Likelihood
ConfidentialityRead Memory

Note: For an out-of-bounds read, the attacker may have access to sensitive information. If the sensitive information contains system details, such as the current buffer's position in memory, this knowledge can be used to craft further attacks, possibly with more severe consequences.
Integrity
Availability		Modify Memory, DoS: Crash, Exit, or Restart

Note: Out of bounds memory access will very likely result in the corruption of relevant memory, and perhaps instructions, possibly leading to a crash.
IntegrityModify Memory, Execute Unauthorized Code or Commands

Note: If the corrupted memory can be effectively controlled, it may be possible to execute arbitrary code. If the corrupted memory is data rather than instructions, the system will continue to function with improper changes, possibly in violation of an implicit or explicit policy.

Observed Examples

References Description

CVE-2002-2227

Unchecked length of SSLv2 challenge value leads to buffer underflow.

CVE-2007-4580

Buffer underflow from a small size value with a large buffer (length parameter inconsistency, CWE-130)

CVE-2007-1584

Buffer underflow from an all-whitespace string, which causes a counter to be decremented before the buffer while looking for a non-whitespace character.

CVE-2007-0886

Buffer underflow resultant from encoded data that triggers an integer overflow.

CVE-2006-6171

Product sets an incorrect buffer size limit, leading to "off-by-two" buffer underflow.

CVE-2006-4024

Negative value is used in a memcpy() operation, leading to buffer underflow.

CVE-2004-2620

Buffer underflow due to mishandled special characters

Detection Methods

Fuzzing

Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.
Effectiveness : High

Vulnerability Mapping Notes

Justification : The CWE entry might be misused when lower-level CWE entries might be available. It also overlaps existing CWE entries and might be deprecated in the future.
Comment : If the "Access" operation is known to be a read or a write, then investigate children of entries such as CWE-787: Out-of-bounds Write and CWE-125: Out-of-bounds Read.

Submission

Name Organization Date Date release Version
CWE Content Team MITRE 2009-10-21 +00:00 2009-10-29 +00:00 1.6

Modifications

Name Organization Date Comment
CWE Content Team MITRE 2011-06-01 +00:00 updated Common_Consequences
CWE Content Team MITRE 2012-05-11 +00:00 updated Common_Consequences, Demonstrative_Examples, Observed_Examples, Relationships
CWE Content Team MITRE 2017-11-08 +00:00 updated Common_Consequences, Demonstrative_Examples, Taxonomy_Mappings
CWE Content Team MITRE 2019-01-03 +00:00 updated Relationships
CWE Content Team MITRE 2020-02-24 +00:00 updated Relationships
CWE Content Team MITRE 2020-08-20 +00:00 updated Relationships
CWE Content Team MITRE 2020-12-10 +00:00 updated Relationships
CWE Content Team MITRE 2023-01-31 +00:00 updated Description
CWE Content Team MITRE 2023-04-27 +00:00 updated Detection_Factors, Relationships
CWE Content Team MITRE 2023-06-29 +00:00 updated Mapping_Notes
CWE Content Team MITRE 2024-02-29 +00:00 updated Demonstrative_Examples
CWE Content Team MITRE 2024-07-16 +00:00 updated Common_Consequences