Adobe Flash Player Use-After-Free
CVE-2016-7855 is a high-severity use after free vulnerability in Flash Player from Adobe, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. Affected Flash Player versions: 23.0.0.185 and earlier; 11.2.202.637 and earlier. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on March 3, 2022, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Check which version of Flash Player you run against the affected versions below, and install the vendor's latest release.
- CISA's required action: The impacted product is end-of-life and should be disconnected if still in use.
- Read the advisory on docs.microsoft.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Adobe | Flash Player | 23.0.0.185 and earlier; 11.2.202.637 and earlier | Not stated |
| Red Hat | Enterprise Linux Desktop | 5.0; 6.0 | Not stated |
| Red Hat | Enterprise Linux Server | 5.0; 6.0 | Not stated |
| Red Hat | Enterprise Linux Workstation | 5.0; 6.0 | Not stated |
Version data comes from NVD's product matching. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.8 | High | NVD |
| CVSS 3.1 | 8.8 | High | CISA (ADP) |
| CVSS 2.0 | 9.3 | High | NVD |
Official description
Use-after-free vulnerability in Adobe Flash Player before 23.0.0.205 on Windows and OS X and before 11.2.202.643 on Linux allows remote attackers to execute arbitrary code via unspecified vectors, as exploited in the wild in October 2016.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- rhn.redhat.com/errata/RHSA-2016-2119.htmlThird Party Advisory
- securityfocus.com/bid/93861Third Party Advisory, VDB Entry
- securitytracker.com/id/1037111Third Party Advisory, VDB Entry
- security.gentoo.org/glsa/201610-10Third Party Advisory
- security.googleblog.com/2016/10/disclosing-vulnerabilities-to-protect.htmlThird Party Advisory
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2016-7855US Government Resource
Other vulnerabilities in Flash Player
- 7.8 High severity
Adobe Flash Player Use-After-Free Exploited
- 7.8 High severity
- 7.8 High severity
Adobe Flash Player Use-After-Free Exploited
- 8.8 High severity
Adobe Flash Player Type Confusion Exploited
- 8.8 High severity
Adobe Flash Player Use-After-Free Exploited
- 9.8 Critical severity
Adobe Flash Player Remote Code Execution Exploited
Recent Use After Free vulnerabilities
- 8.8 High severity
- 9.8 Critical severity
Adobe Flash Player Use-After-Free Exploited
- 9.8 Critical severity
Adobe Flash Player Use-After-Free Exploited
- 9.8 Critical severity
Adobe Flash Player Use-After-Free Exploited
- 9.8 Critical severity
Adobe Flash Player Use-After-Free Exploited
- 10.0 High severity
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