High severity · published Feb 26, 2021
CVE-2021-21309
Redis is an open-source, in-memory database that persists on disk
8.8
CVSS
4.8%
EPSS
No
On KEV
Description
Redis is an open-source, in-memory database that persists on disk. In affected versions of Redis an integer overflow bug in 32-bit Redis version 4.0 or newer could be exploited to corrupt the heap and potentially result with remote code execution. Redis 4.0 or newer uses a configurable limit for the maximum supported bulk input size. By default, it is 512MB which is a safe value for all platforms. If the limit is significantly increased, receiving a large request from a client may trigger several integer overflow scenarios, which would result with buffer overflow and heap corruption. We believe this could in certain conditions be exploited for remote code execution. By default, authenticated Redis users have access to all configuration parameters and can therefore use the “CONFIG SET proto-max-bulk-len” to change the safe default, making the system vulnerable. **This problem only affects 32-bit Redis (on a 32-bit system, or as a 32-bit executable running on a 64-bit system).** The problem is fixed in version 6.2, and the fix is back ported to 6.0.11 and 5.0.11. Make sure you use one of these versions if you are running 32-bit Redis. An additional workaround to mitigate the problem without patching the redis-server executable is to prevent clients from directly executing `CONFIG SET`: Using Redis 6.0 or newer, ACL configuration can be used to block the command. Using older versions, the `rename-command` configuration directive can be used to rename the command to a random string unknown to users, rendering it inaccessible. Please note that this workaround may have an additional impact on users or operational systems that expect `CONFIG SET` to behave in certain ways.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)4.8% · higher than 92% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RE
Redis · Redis
4.0 before 5.0.11; 6.0.0 before 6.0.11 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-21309
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-21309
Patch
https://github.com/redis/redis/commit/c992857618db99776917f10bf4f2345a5fdc78b0
Patch
https://github.com/redis/redis/pull/8522
Third Party Advisory
https://github.com/redis/redis/security/advisories/GHSA-hgj8-vff2-7cjf
Third Party Advisory
https://security.gentoo.org/glsa/202103-02
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