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Actively exploited

CVE-2015-5123 Adobe Flash Player Use-After-Free Vulnerability

Use-after-free vulnerability in the BitmapData class in the ActionScript 3 (AS3) implementation in Adobe Flash Player allows remote attackers to execute code or cause a denial-of-service (DoS).

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 13 Apr 2022.
  • Rated High severity (CVSS 7.8, scored by CISA).
  • It has been in the catalogue for 1,668 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

Use-after-free vulnerability in the BitmapData class in the ActionScript 3 (AS3) implementation in Adobe Flash Player 13.x through 13.0.0.302 on Windows and OS X, 14.x through 18.0.0.203 on Windows and OS X, 11.x through 11.2.202.481 on Linux, and 12.x through 18.0.0.204 on Linux Chrome installations allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via crafted Flash content that overrides a valueOf function, as exploited in the wild in July 2015.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Adobe Flash Player. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    The impacted product is end-of-life and should be disconnected if still in use.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 4 May 2022 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Adobe Flaws

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Not Sure If You Are Exposed?

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2015-5123
  3. CVE record: CVE-2015-5123
  4. FIRST EPSS
  5. securitytracker.com/id/1032890
  6. lists.opensuse.org/opensuse-security-announce/2015-07/msg00028.html
  7. blog.trendmicro.com/trendlabs-security-intelligence/new-zero-day-vulnerability-cve-2015-5123-in-adob
  8. marc.info/?l=bugtraq&m=144050155601375&w=2
  9. us-cert.gov/ncas/alerts/TA15-195A
  10. helpx.adobe.com/security/products/flash-player/apsb15-18.html
  11. kb.cert.org/vuls/id/918568
  12. lists.opensuse.org/opensuse-security-announce/2015-07/msg00029.html