CVE-2021-32675 | DoS vulnerability in Redis

Redis is an open source, in-memory database that persists on disk. When parsing an incoming Redis Standard Protocol (RESP) request, Redis allocates memory according to user-specified values which determine the number of elements (in the multi-bulk header) and size of each element (in the bulk header). An attacker delivering specially crafted requests over multiple connections can cause the server to allocate significant amount of memory. Because the same parsing mechanism is used to handle authentication requests, this vulnerability can also be exploited by unauthenticated users. The problem is fixed in Redis versions 6.2.6, 6.0.16 and 5.0.14. An additional workaround to mitigate this problem without patching the redis-server executable is to block access to prevent unauthenticated users from connecting to Redis. This can be done in different ways: Using network access control tools like firewalls, iptables, security groups, etc. or Enabling TLS and requiring users to authenticate using client side certificates.

Published: 2021-10-04 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-32675 is rated High Risk (68.8/100): CVSS High severity, with high exploitation likelihood (EPSS 15.78%, 96th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +9.94% over the last day, indicating growing attacker interest. High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-32675

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 5.84% 15.78% +9.94%
2 2026-06-06 2.85% 5.84% +2.98%
3 2026-04-19 — 2.85% —

Full EPSS history (35 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-32675

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-32675

OS Trackers for CVE-2021-32675

vendor priority summary link
alpine high CVE-2021-32675: 1 source package rows (redis); 34 state rows across 10 repos (3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-community, 3.21-community, 3.22-community, edge-community, edge-main); fixed 10, open 24. https://security.alpinelinux.org/vuln/CVE-2021-32675
debian not yet assigned CVE-2021-32675 not yet assigned priority: Debian including 1 source packages (redis), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-32675
gentoo high CVE-2021-32675: 1 GLSA(s) (202209-17), 1 atom(s) (dev-db/redis); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-32675
redhat high — https://access.redhat.com/security/cve/CVE-2021-32675
suse high CVE-2021-32675 severity important: SUSE including 7 source package names (redis, redis-6.0.14-6.8.1, …), 9 product×package rows across 6 product lines (SUSE Liberty Linux 8, SUSE Linux Enterprise Module for Server Applications 15 SP2, … (6 product lines)): Fixed 8, Known Not Affected 1. https://www.suse.com/security/cve/CVE-2021-32675/
ubuntu medium CVE-2021-32675 medium priority: Ubuntu including 1 source packages (redis), 14 status rows across 14 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): not-affected 7, released 5, ignored 2. https://ubuntu.com/security/CVE-2021-32675

Affected software / configurations for CVE-2021-32675

Vendor Product Version Raw CPE
redis redis >= 5.0.0, < 5.0.14 cpe:2.3:a:redis:redis:*:*:*:*:*:*:*:*
redis redis >= 6.0.0, < 6.0.16 cpe:2.3:a:redis:redis:*:*:*:*:*:*:*:*
redis redis >= 6.2.0, < 6.2.6 cpe:2.3:a:redis:redis:*:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
netapp management_services_for_element_software — cpe:2.3:a:netapp:management_services_for_element_software:-:*:*:*:*:*:*:*
netapp management_services_for_netapp_hci — cpe:2.3:a:netapp:management_services_for_netapp_hci:-:*:*:*:*:*:*:*
oracle communications_operations_monitor 4.3 cpe:2.3:a:oracle:communications_operations_monitor:4.3:*:*:*:*:*:*:*
oracle communications_operations_monitor 4.4 cpe:2.3:a:oracle:communications_operations_monitor:4.4:*:*:*:*:*:*:*
oracle communications_operations_monitor 5.0 cpe:2.3:a:oracle:communications_operations_monitor:5.0:*:*:*:*:*:*:*

References for CVE-2021-32675

URL Tags
https://github.com/redis/redis/commit/5674b0057ff2903d43eaff802017eddf37c360f8 Patch Third Party Advisory
https://github.com/redis/redis/security/advisories/GHSA-f6pw-v9gw-v64p Third Party Advisory
https://lists.apache.org/thread.html/ra603ff6e04549d7f290f61f9b11e2d2e4dba693b05ff053f4ec6bc47%40%3Cnotifications.geode.apache.org%3E
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HTYQ5ZF37HNGTZWVNJD3VXP7I6MEEF42/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VL5KXFN3ATM7IIM7Q4O4PWTSRGZ5744Z/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WR5WKJWXD4D6S3DJCZ56V74ESLTDQRAB/
https://security.gentoo.org/glsa/202209-17 Third Party Advisory
https://security.netapp.com/advisory/ntap-20211104-0003/ Third Party Advisory
https://www.debian.org/security/2021/dsa-5001 Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html Patch Third Party Advisory
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