CVE-2021-21017 / Adobe APSB21-09: Adobe Acrobat and Reader Heap-based Buffer Overflow Vulnerability

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CISA confirms exploitation in the wild and lists 2021-11-17 as the remediation due date.

Fix not verified

What, why and how

Acrobat Acrobat and Reader contain a heap-based buffer overflow vulnerability that could allow an unauthenticated attacker to achieve code execution in the context of the current user.

What

Acrobat Acrobat and Reader contain a heap-based buffer overflow vulnerability that could allow an unauthenticated attacker to achieve code execution in the context of the current user.

Why

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

How

An attacker operating through a network path may attempt exploitation without authentication after a user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

Acrobat Acrobat and Reader contain a heap-based buffer overflow vulnerability that could allow an unauthenticated attacker to achieve code execution in the context of the current user.

Why

How

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation

Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.

Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2021-11-03.

Public PoC / exploit material

Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.

None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path: a network path → Heap-based Buffer Overflow → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface: Network
Privileges required: None: unauthenticated exploitation is possible
User interaction: Required interaction required
Attack complexity: Low: no specialised conditions are recorded
Security boundary: Unchanged: impact remains within the vulnerable component's security authority
Weakness ? CWE means Common Weakness Enumeration: a standard category for the underlying weakness.: CWE-122 ↗
CWE-122: Heap-based Buffer Overflow. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
CVSS vector ? CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land: No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.

NetworkUnauthenticatedCWE-122CISA KEV

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2021-8423Known-exploited evidence recorded

Acrobat Reader DC versions versions 2020.013.20074 (and earlier), 2020.001.30018 (and earlier) and 2017.011.30188 (and earlier) are affected by a heap-based buffer overflow vulnerability. An unauthenticated attacker could leverage this vulnerability to achieve arbitrary code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.

Official EUVD record ↗

Cyber Security Agency of Singapore · English · CSA-SB-20210217Security Bulletin 17 Feb 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 17 Feb 2021, published on 17 February 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Adobe Acrobat and Reader Heap-based Buffer Overflow Vulnerability

Evidence used

Compensating controls

Verification

EUVD-2021-8423

What, why and how

Exploit reality and attack path

Official authority intelligence

Patch and workaround

Evidence and provenance