CVE-2021-32761

Redis is an in-memory database that persists on disk. A vulnerability involving out-of-bounds read and integer overflow to buffer overflow exists starting with version 2.2 and prior to versions 5.0.13, 6.0.15, and 6.2.5. On 32-bit systems, Redis *BIT* command are vulnerable to integer overflow that can potentially be exploited to corrupt the heap, leak arbitrary heap contents or trigger remote code execution. The vulnerability involves changing the default proto-max-bulk-len configuration parameter to a very large value and constructing specially crafted commands bit commands. This problem only affects Redis on 32-bit platforms, or compiled as a 32-bit binary. Redis versions 5.0.3m 6.0.15, and 6.2.5 contain patches for this issue. An additional workaround to mitigate the problem without patching the redis-serverexecutable is to prevent users from modifying theproto-max-bulk-len` configuration parameter. This can be done using ACL to restrict unprivileged users from using the CONFIG SET command.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Name	Vendor	Start Version	End Version
Redis	Redislabs	2.2.0 (including)	5.0.13 (excluding)
Redis	Redislabs	6.0 (including)	6.0.15 (excluding)
Redis	Redislabs	6.2.0 (including)	6.2.5 (excluding)
Redis	Ubuntu	bionic	*
Redis	Ubuntu	esm-apps/bionic	*
Redis	Ubuntu	esm-apps/xenial	*
Redis	Ubuntu	groovy	*
Redis	Ubuntu	impish	*
Redis	Ubuntu	trusty	*
Redis	Ubuntu	trusty/esm	*
Redis	Ubuntu	upstream	*
Redis	Ubuntu	xenial	*

Potential Mitigations

Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

https://cwe.mitre.org/data/definitions/540.html

NVD	https://nvd.nist.gov/vuln/detail/CVE-2021-32761
CWE	https://cwe.mitre.org/data/definitions/125.html

Out-of-bounds Read

Weakness

Affected Software

Potential Mitigations

References

CVE-2021-32761

Out-of-bounds Read

Weakness

Affected Software

Potential Mitigations

Related Attack Patterns

References