Cisco Email Security Appliance and Cisco Content Security Management Appliance Denial of Service Vulnerability
A vulnerability in the email message filtering feature of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) and Cisco Content Security Management Appliance (SMA) could allow an unauthenticated, remote attacker to cause repeated crashes in some internal processes that are running on the affected devices, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient input validation of email attachments. An attacker could exploit this vulnerability by sending an email message with a crafted attachment through an affected device. A successful exploit could allow the attacker to cause specific processes to crash repeatedly, resulting in the complete unavailability of both the Cisco Advanced Malware Protection (AMP) and message tracking features and in severe performance degradation while processing email. After the affected processes restart, the software resumes filtering for the same attachment, causing the affected processes to crash and restart again. A successful exploit could also allow the attacker to cause a repeated DoS condition. Manual intervention may be required to recover from this situation.
- Published
- Sep 22, 2020
- Updated
- Jun 16, 2026
- EPSS
- 1.9% · 78th percentile
- CWE
- CWE-20
Sign in to follow · You’ll be notified if a followed record enters KEV, gets an exploit or is updated.
Report tools
Action score
22
Monitor
Low priority for now.
- CVSS
- 21 / 40 · 5.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 1.9%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 5.3
- CNA · cisco
- 7.5
- 2.2 point gap
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| cisco | content security management appliance | cpe:2.3:a:cisco:content_security_management_appliance |
| cisco | asyncos | cpe:2.3:o:cisco:asyncos |
| cisco | email security appliance | cpe:2.3:a:cisco:email_security_appliance |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- cisco asyncosbefore 11.0.3-251
- cisco asyncosbefore 11.0.1-161
- cisco asyncos12.0 and later · up to 12.5.0-633 inclusive
- cisco asyncos12.0 and later · before 12.5.0-059
- cisco content security management appliance11.4.0-812
- cisco email security appliance11.0.1-hp5-602
- cisco email security appliance11.1.0-404
Versions reported by the vendor
Affected version ranges reported by the assigning authority (cisco). Independent of NVD's CPE analysis and usually ahead of it.
Cisco Cisco Email Security Appliance (ESA)
- n/aaffected
Same product
cisco: all recordsOther highest-scoring records for the same primary product.
- CVE-2013-3395Cross-site request forgery (CSRF) vulnerability in the web framework on Cisco IronPort Web Security Appliance (WSA) devices, Email Security 27Monitor
- CVE-2021-1516Cisco Content Security Management Appliance, Email Security Appliance, and Web Security Appliance Information Disclosure Vulnerability26Monitor
- CVE-2021-1447Cisco Content Security Management Appliance Privilege Escalation Vulnerability26Monitor
- CVE-2020-3447Cisco Email Security Appliance and Cisco Content Security Management Appliance Information Disclosure Vulnerability26Monitor
- CVE-2020-3178Cisco Content Security Management Appliance Open Redirect Vulnerabilities24Monitor
- CVE-2018-15393Cisco Content Security Management Appliance (SMA) Cross-Site Scripting Vulnerability24Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
No fix version is recorded for this entry. Check the references for vendor advisories.
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- low · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- Low
Weakness class (CWE)
CWE-20 · Improper Input ValidationCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Buffer Overflow via Environment VariablesCAPEC-10likelihood: High · High
- Server Side Include (SSI) InjectionCAPEC-101likelihood: High · High
- Cross Zone ScriptingCAPEC-104likelihood: Medium · High
- Command Line Execution through SQL InjectionCAPEC-108likelihood: Low · Very High
- Object Relational Mapping InjectionCAPEC-109likelihood: Low · High
- SQL Injection through SOAP Parameter TamperingCAPEC-110likelihood: High · Very High
- Double EncodingCAPEC-120likelihood: Low · Medium
- Subverting Environment Variable ValuesCAPEC-13likelihood: High · Very High
ATT&CK techniques
- Obfuscated Files or InformationT1027
- Masquerading: Invalid Code SignatureT1036.001
- Steal Web Session CookieT1539
- Subvert Trust Controls: Code SigningT1553.002
- Impair Defenses:Impair Command History LoggingT1562.003
- Hijack Execution Flow:Dynamic Linker HijackingT1574.006
- Hijack Execution Flow:Path Interception by PATH Environment VariableT1574.007
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.
References
Vendor advisories and official records. Exploit/PoC links are deliberately left out.