Threats / Arm / CVE-2021-27562
CVE-2021-27562
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
Arm Trusted Firmware vulnerability
Arm Trusted Firmware contains an out-of-bounds write vulnerability (CWE-787) in the non-secure processing environment handler that allows attackers to trigger system halt, overwrite secure data, or leak sensitive information.
Verdict
Today item — known-exploited.
An out-of-bounds write in Arm Trusted Firmware's NSPE handler permits non-secure code to corrupt secure memory, halt the system, or exfiltrate protected data. Active exploitation in the wild demonstrates practical attack feasibility.
CISA KEV Yes · 2021-11-034EPSS 0.03093 (verify live)5CVSS 5.5 (CISA)3CISA SSVC Exploitation: active · Automatable: no · Impact: partial3
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
5 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03).
Probability (EPSS)
EPSS 0.03093 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) · Affected: Arm, Trusted Firmware. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-787 Out-of-bounds Write — weakness family: Memory safety.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 162 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I execute untrusted code in the non-secure world and invoke secure functions through the NSPE handler.
Business
System availability is compromised through denial-of-service halts triggered from unprivileged execution contexts.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I craft malicious non-secure function calls that write out-of-bounds into secure memory regions.
Business
Confidentiality and integrity of secure firmware and cryptographic keys are breached, undermining the trusted execution environment.
3
Lateral reach — past segmentation narrative 3
Attacker
I leverage the out-of-bounds write to read and exfiltrate secure data stored in protected memory.
Business
Sensitive authentication credentials and security-critical data are exposed to attackers with non-secure access.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by mitreCNA
Credited with finding itNo finder is named in the public CVE record or the scanned vendor advisory — attribution scoped to the sources checked.
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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