CVE-2021-20266

A flaw was found in RPM's hdrblobInit() in lib/header.c. This flaw allows an attacker who can modify the rpmdb to cause an out-of-bounds read. The highest threat from this vulnerability is to system availability.

Published: 2021-04-30 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-20266 is rated Moderate Risk (47.5/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.75%). EPSS rose +1.69% over the last day, indicating growing attacker interest. Review affected assets and schedule 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-2021-20266

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 0.06% 1.75% +1.69%
2 2025-11-21 0.50% 0.06% -0.43%
3 2025-11-18 — 0.50% —

Full EPSS history (13 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-20266

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.9 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:H/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:H)
They need powerful rights—admin, root, or similar—before this pays off.
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.
 1.2 3.6 [email protected]
4.0 2.0 MEDIUM
AV:N/AC:L/Au:S/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:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 2.9 [email protected]

Weakness enumeration for CVE-2021-20266

OS Trackers for CVE-2021-20266

vendor priority summary link
alpine medium CVE-2021-20266: 1 source package rows (rpm); 10 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 10, open 0. https://security.alpinelinux.org/vuln/CVE-2021-20266
debian not yet assigned CVE-2021-20266 not yet assigned priority: Debian including 1 source packages (rpm), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-20266
gentoo normal CVE-2021-20266: 1 GLSA(s) (202107-43), 1 atom(s) (app-arch/rpm); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-20266
redhat low — https://access.redhat.com/security/cve/CVE-2021-20266
suse low CVE-2021-20266 severity low: SUSE including 146 source package names (0.21.0.3.2.10:rpm-ndb-4.14.3-37.2, 0.7.1-rev1.0.0-build2.2.1:python3-rpm-4.14.3-37.2, …), 366 product×package rows across 178 product lines (Container bci/bci-init, Container bci/bci-minimal, … (178 product lines)): Fixed 366. https://www.suse.com/security/cve/CVE-2021-20266/
ubuntu low CVE-2021-20266 low priority: Ubuntu including 1 source packages (rpm), 15 status rows across 15 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): not-affected 9, ignored 3, released 3. https://ubuntu.com/security/CVE-2021-20266

Affected software / configurations for CVE-2021-20266

Vendor Product Version Raw CPE
rpm rpm < 4.16.1.3 cpe:2.3:a:rpm:rpm:*:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

References for CVE-2021-20266

cvelogic Threat Intelligence