Three Zoom annotation bugs made every screen share a two-way takeover path
Client fixes shipped in June and July. The exploit route only went public this month, and Zoom scores the bugs well below the firm that found them.
The Watch · Security desk
What happened
- The flaws sat in Zoom's annotation tool, the feature that lets participants draw and type on a shared screen.
- Anyone sharing their screen on a Zoom call could have taken over the computers of everyone watching, and anyone watching could have taken over the presenter's; the flaw asked nothing of the victim beyond being in the meeting, with no click, no download, no prompt and nothing on screen to show it had happened.
- Client fixes shipped in June and July, roughly two months before the flaws were made public.
- Fixed versions: Zoom Workplace, all supported platforms, before 7.1.5 and 7.0.6 in their respective branches; Zoom Workplace VDI Client for Windows, before 7.0.11 and 6.6.16; Zoom Rooms and Zoom Meeting SDK, all platforms, before 7.1.0, and before 7.1.5 for the third flaw.
- SecurityAffairs reported that "this week, Zoom released Workplace versions 7.1.5 and 7.0.6, Rooms version 7.1.5, and Meeting SDK version 7.1.5 for all supported platforms" to address the vulnerabilities.
Why it matters
Zoom has patched three flaws in the annotation tool, the feature that lets participants draw on a shared screen, that on the paths researchers traced allowed a viewer to run code on the presenter's machine and the presenter to run code on every viewer's [1][22]. The client fixes shipped in June and July, roughly two months before the write-up that made the mechanism public, so any fleet still on an older build is now behind a documented route rather than a theoretical one [23].
The versions that close the set: Zoom Workplace on all supported platforms before 7.1.5 and 7.0.6 in their respective branches; the Workplace VDI Client for Windows before 7.0.11 and 6.6.16; Zoom Rooms and the Zoom Meeting SDK before 7.1.0, and before 7.1.5 for the third flaw [2]. SecurityAffairs described the Workplace 7.1.5 and 7.0.6, Rooms 7.1.5 and Meeting SDK 7.1.5 releases as landing "this week," which does not sit cleanly beside the June and July timeline reported by The Hacker News [3][23]. No exploitation has been reported, and none of the three identifiers is in CISA's Known Exploited Vulnerabilities catalog [15].
Zoom has published no technical detail, so the internals come from the reverse engineering done by A Security, the Israeli-founded offensive-security startup that left stealth in June with $37 million [4][5]. A drawing does not cross the wire as an image: the client serialises it into a structured object sent as a run of counts followed by data, and the receiver trusts those counts to decide how much to read [6]. One field fills a fixed 128-byte buffer with no length check, and because it is the object's last field, an oversized count runs past the end and over the return address [7]. The bug sits in CAnnoFormatBlock::Deserialize in libannotate.so, reachable through Zoom's normal encrypted transport [8].
What turns one malformed drawing into a room-wide problem is a missing origin check. Every viewer holds a channel to the sharer and the sharer holds one back for acknowledgements; the dispatcher reads the type number off the wire and hands it to the matching parser without asking which seat the sender occupied [9]. 0x10001 means here is an object, 0x10002 means I received yours, and sending the first where the second belongs makes the victim's client rebuild the object in full [10].
The two accounts of severity diverge. Zoom tracks CVE-2026-53413 at CVSS 8.3, CVE-2026-53414 at 6.5 and CVE-2026-53415 at 8.3 [16]; A Security puts all three at 9.0 under CVSS 4.0, a figure in none of the bulletins [17]. Zoom issues its own CVE records and NIST no longer routinely re-scores them, so the lower numbers will likely stand [28]. All three vendor vectors also mark user interaction as required, which is hard to reconcile with the zero-click framing [11]. On the over-read, the firm says it recovered uninitialised heap memory holding live code and vtable pointers, the material an address-randomisation bypass needs; the advisory says the bug may allow denial of service and scores confidentiality impact at none [24][25]. Credit splits too: two bulletins name Idan Levcovich of A Security, while the use-after-free is credited to Zoom Offensive Security, the in-house team behind the 9.8-rated account takeover flaw patched in July [12][13].
Treat the AI framing carefully. The firm says it went from flaw to working exploit in under a day using fewer than 20 prompts on publicly available models, but names no model, and its own account is messier: the automated first pass produced a queue of 3,762 functions across 70 libraries and ranked the vulnerable library 45th, surfacing only under live dynamic tracing [26][27][14].
Watch whether Zoom or NIST revises the scores, whether the identifiers reach KEV, and whether your VDI estate got the 7.0.11 and 6.6.16 builds, which are easy to miss when the headline number is 7.1.5 [2].
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence70
- Adoption52
- Hype gap+34
- Incentives74
- Confidence68
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
The flaws sat in Zoom's annotation tool, the feature that lets participants draw and type on a shared screen.
- [2]
Fixed versions: Zoom Workplace, all supported platforms, before 7.1.5 and 7.0.6 in their respective branches; Zoom Workplace VDI Client for Windows, before 7.0.11 and 6.6.16; Zoom Rooms and Zoom Meeting SDK, all platforms, before 7.1.0, and before 7.1.5 for the third flaw.
- [3]
SecurityAffairs reported that "this week, Zoom released Workplace versions 7.1.5 and 7.0.6, Rooms version 7.1.5, and Meeting SDK version 7.1.5 for all supported platforms" to address the vulnerabilities.
- [4]
Zoom has published no technical detail, so the internals come from A Security's own reverse engineering.
- [5]
The research came from "A Security," an Israeli-founded offensive-security startup that left stealth in June with $37 million in funding.
- [6]
A drawing does not cross the network as a picture: the client turns it into a structured object and sends it as a run of counts followed by data, and the receiver trusts those counts to decide how much to read.
- [7]
One field fills a fixed 128-byte buffer with no check that the data fits, and because it is the object's last field, an oversized count runs past the end and over the return address.
- [8]
CVE-2026-53413 is a remotely triggerable stack buffer overflow in CAnnoFormatBlock::Deserialize; dynamic tracing identified libannotate.so and its proprietary annotation protocol, and the flaw is reachable through Zoom's normal encrypted transport with no victim interaction or instrumentation.
- [9]
Every viewer holds a channel to whoever is sharing and the sharer holds one back meant to carry acknowledgements; on the paths the researchers traced, the dispatcher reads a message's type number off the wire and hands it to the matching parser without checking which seat the sender occupied.
- [10]
0x10001 means here is an object and 0x10002 means I received yours; sending the first where the second belongs makes the victim's client rebuild the object in full.
- [11]
All three vendor CVSS vectors mark user interaction as required, which sits badly beside the zero-click framing.
- [12]
Two bulletins name Idan Levcovich of A Security, while the bulletin covering the use-after-free credits Zoom Offensive Security, the in-house team behind the 9.8-rated account takeover flaw the company patched in July.
- [13]
A Security's post lists all three flaws as its own while acknowledging that Zoom already knew about the third and had filtered it server-side before the report arrived.
- [14]
The first pass, an automated ranking of functions reachable from the Java layer, produced a queue of 3,762 functions across 70 libraries and missed the vulnerable library completely, ranking it 45th; it surfaced only when researchers traced the running client through a live call, feature by feature.
- [15]
No exploitation has been reported as of publication, and none of the three identifiers appears in CISA's Known Exploited Vulnerabilities catalog.
- [16]
Zoom tracks the flaws as CVE-2026-53413 (CVSS 8.3, buffer over-write) and CVE-2026-53414 (CVSS 6.5, buffer over-read), both covered by ZSB-26015 and ZSB-26016, plus CVE-2026-53415 (CVSS 8.3, use-after-free) in ZSB-26017.
- [17]
A Security puts all three flaws at 9.0 under CVSS 4.0, a score that appears in none of Zoom's bulletins.
- [18]
Levcovich writes that the barrier to building this class of exploit "has collapsed, and it will not come back."
- [19]
The disclosure follows OpenAI splitting its Daybreak program a day earlier and releasing GPT-5.6-Cyber to vetted partners only, on the argument that this capability needs gating.
- [20]
Researchers dubbed CVE-2026-53413 "Zoomsday"; Zoom's Android client was chosen as a target because it is closed-source, widely deployed and exposes a large native-code attack surface.
- [21]
The gap between Zoom's highest score for the set and A Security's score is 0.7 points.
- [22]
Anyone sharing their screen on a Zoom call could have taken over the computers of everyone watching, and anyone watching could have taken over the presenter's; the flaw asked nothing of the victim beyond being in the meeting, with no click, no download, no prompt and nothing on screen to show it had happened.
- [23]
Client fixes shipped in June and July, roughly two months before the flaws were made public.
- [24]
A Security says it recovered uninitialized heap memory from a victim's client holding live code and vtable pointers, the material an address-randomization bypass needs.
- [25]
Zoom's advisory says the over-read bug may let a participant "conduct a denial of service" and scores its confidentiality impact at none.
- [26]
A Security says it went from finding the flaw to a working exploit in under a day, using fewer than 20 prompts on publicly available AI models.
- [27]
Nobody outside the company can check the AI claim: the writeup names no model.
- [28]
Zoom issues its own CVE records and NIST no longer routinely re-scores them, so the lower figures will likely stand.
Sources
2 independent publishers whose own reporting we read for this story.
- securityaffairs.comZoom Patches “Zoomsday” Zero-Click Flaw Enabling Remote Code Execution
1 article · August 11, 2026
- thehackernews.comZoom Annotation Flaws Could Let a Meeting Participant Hijack Another Attendee's Client
1 article · August 11, 2026
Topics and entities
Topics
- Real-Time Collaboration and Conferencing Security
- Enterprise Patch Management
- AI-Assisted Exploit Development
- Vulnerability Disclosure and CVSS Scoring
- Memory Safety in Native Client Code
Entities
- Zoom Meeting SDK
- OpenAI
- Daybreak
- CISA Known Exploited Vulnerabilities Catalog
- ZSB-26015 / ZSB-26016 / ZSB-26017
- GPT-5.6-Cyber
- Zoom Offensive Security
- Zoom