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CVE-2021-27433

32
FAUCET Score

CVE-2021-27433 is a critical integer wrap-around vulnerability in the ARM mbed-ualloc memory library version 1.3.0, specifically within the mbed_krbs function. This flaw can lead to arbitrary memory allocation, potentially causing system crashes or enabling remote code injection/execution. With a CVSS score of 9.8 (CRITICAL), it is easily exploitable over the network with low attack complexity and no user interaction, allowing for high impact on confidentiality, integrity, and availability. While there is no evidence of active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has garnered significant community discussion, indicating awareness among security researchers.

Impacted Technologies

VendorProductVersion(s)CPE
1.3.0CPE matchmatch criteria
cpe:2.3:a:arm:mbed_ualloc:1.3.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.3HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
LOW
Exploitability Score
3.9
Impact Score
3.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.68%
Probability of exploitation in next 30 days
EPSS Percentile
74.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0168 is in the 62nd percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / ARMmbed/mbed-os/pull/14408
Issue TrackingPatchThird Party Advisory
cisa.gov / uscert/ics/advisories/icsa-21-119-04
Third Party AdvisoryUS Government Resource