Zoom Annotation Flaws Could Let a Meeting Participant Hijack Another Attendee's Client
A Security researchers disclosed three Zoom annotation flaws enabling zero-click client hijacking; Zoom shipped fixes in June and July with no exploitation reported.
Researchers at A Security found three flaws in Zoom's annotation feature: CVE-2026-53413 (CVSS 8.3, buffer over-write), CVE-2026-53414 (CVSS 6.5, buffer over-read), and CVE-2026-53415 (CVSS 8.3, use-after-free). A crafted drawing object sent over the wrong message channel can overwrite adjacent memory and hijack another attendee's client with no user interaction. Fixes shipped in Zoom Workplace 7.1.5/7.0.6, VDI Client 7.0.11/6.6.16, and Zoom Rooms/Meeting SDK 7.1.0+ during June and July. No exploitation has been reported and the flaws are absent from CISA's Known Exploited Vulnerabilities catalog.
- CVE-2026-53413 (CVSS 8.3) buffer over-write and CVE-2026-53414 (CVSS 6.5) over-read; researcher-rated 9.0 under CVSS 4.0
- Malformed drawing object accepted without origin check overruns a fixed 128-byte buffer
- Fixes shipped in Workplace 7.1.5/7.0.6, VDI 7.0.11/6.6.16, Rooms and SDK 7.1.0+
- No exploitation reported; none of the three identifiers appear in CISA's KEV catalog
- A Security claims the exploit was built in under a day using fewer than 20 prompts on public AI models
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2026-53413 | Out-of-Bounds Write in Zoom Clients Enables Participant-to-Participant RCE Zoom has fixed an out-of-bounds write (CWE-787) in the annotator function of its client applications, tracked as CVE-2026-53413. A meeting participant can trigger the missing bounds check remotely through the annotation feature, causing a buffer over-write in another attendee's client; per the CVSS vector, user interaction and high attack complexity are required. Successful exploitation may allow the attacker to execute code on the victim's machine with that user's privileges, effectively hijacking another participant's client from within the same meeting. Anyone running a vulnerable Zoom Client (the platform's desktop and mobile apps, used by an extremely large user base) is potentially affected until patched. There is no public proof-of-concept, the flaw is not yet in CISA's KEV catalog, and no exploitation in the wild is known, though an EPSS of 5.6% (92nd percentile) indicates meaningful exploitation potential. Do: Update Zoom Clients to the patched release identified in Zoom's advisory for CVE-2026-53413 and verify installed client versions across managed endpoints. Until patched, limit annotation privileges in meetings to trusted participants and treat meetings with untrusted external attendees as elevated risk. Monitor Zoom's advisory for exact affected/fixed version ranges, since no public PoC exists but EPSS suggests elevated exploitation likelihood. | 8.3 | 6% |
| masswell over 1,000,000 users | ||
| CVE-2026-53414 | Missing bounds check in the annotator function of Zoom Clients allows buffer over-read, which may allow a meeting participant to conduct a denial of service on Missing bounds check in the annotator function of Zoom Clients allows buffer over-read, which may allow a meeting participant to conduct a denial of service on another participant via network access. NVD description · AI analysis pending | 6.5 | <1% | — | — | ||
| CVE-2026-53415 | Use-After-Free in Zoom Client Annotator Enables Participant-to-Participant RCE CVE-2026-53415 is a use-after-free vulnerability (CWE-416) in the annotator function of Zoom Clients, scored 8.3 (High) with a network attack vector and changed scope. It is triggered when one meeting participant sends crafted annotation input that another participant's Zoom client processes, allowing an attacker in the meeting to corrupt memory in a fellow attendee's client; the CVSS vector marks user interaction as required and attack complexity as high, while press coverage describes the flaw as zero-click for the victim. A successful attack yields remote code execution on the other participant's client, with high impact to confidentiality, integrity, and availability. Anyone using Zoom Clients who joins meetings with untrusted participants where annotation is available is potentially affected. Exploitation status: not in CISA KEV, no public PoC, EPSS estimates only a 0.5% probability of exploitation in the next 30 days (44th percentile), and Zoom has already patched the flaw. Do: Update all Zoom desktop and mobile clients to the latest patched release per Zoom's advisory for CVE-2026-53415 (the source data does not list specific fixed version numbers). As an interim mitigation, restrict or disable participant annotation in meeting settings, and prioritize updates for users who routinely join meetings with external or untrusted participants. Check Zoom's bulletin for the fixed version applicable to each client platform in your fleet. | 8.3 | <1% |
| mass≥100M users (Zoom's global client install base) |
Full article813 words · extracted from thehackernews.com · click to collapse
Swati KhandelwalAug 11, 2026Vulnerability / Software Security
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 sat in the annotation tool, the feature that lets participants draw and type on a shared screen, and it asked nothing of the victim beyond being in the meeting. No click, no download, no prompt, and nothing on screen to show it had happened.
The patches are not new. Client fixes shipped in June and July, roughly two months before the flaws were made public, and no exploitation has been reported as of publication. None of the three identifiers appear in CISA's Known Exploited Vulnerabilities catalog.
The versions that close them:
- 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
The research came from "A Security," an Israeli-founded offensive-security startup that left stealth in June with $37 million in funding. It 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.
Nobody outside the company can check that claim: the writeup names no model. The vendor also rates the bugs lower than the firm does, and credits one of the three to its own internal team.
Zoom has published no technical detail, so the internals come from the firm's own reverse engineering. 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.
One of them 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.
What makes one malformed drawing reach the whole room is a missing check on where a message came from. Every viewer holds a channel to whoever is sharing, and the sharer holds one back that is 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 asking which seat the sender occupied. 0x10001 means here is an object; 0x10002 means I received yours. Send the first where the second belongs, and the victim's client rebuilds the object in full.
Zoom tracks the flaws as CVE-2026-53413 (CVSS score: 8.3), a buffer over-write, and CVE-2026-53414 (CVSS score: 6.5), a buffer over-read, both covered by ZSB-26015 and ZSB-26016, plus CVE-2026-53415 (CVSS score: 8.3), a use-after-free, in ZSB-26017.
The firm puts all three at 9.0 under CVSS 4.0, a score that appears in none of the bulletins. Zoom issues its own CVE records, and NIST no longer routinely re-scores them, so the lower figures will likely stand. All three vendor vectors also mark user interaction as required, which sits badly beside the zero-click framing.
The two accounts diverge furthest on the over-read. The firm says it recovered uninitialized heap memory from a victim's client holding live code and vtable pointers, the material an address-randomization bypass needs.
The advisory says the same bug may let a participant "conduct a denial of service," and scores its confidentiality impact at none. Credit splits as well: two bulletins name Idan Levcovich of A Security, while the one 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.
The startup's post lists all three as its own, while acknowledging that Zoom already knew about the third and had filtered it server-side before the report arrived. Its account of the AI work is also messier than its own summary.
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 they traced the running client through a live call, feature by feature. Levcovich writes that the barrier to building this class of exploit "has collapsed, and it will not come back."
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. The startup says it got its result from models anyone can use. By OpenAI's own measure, its guardrailed public model answers 1.5% of advanced offensive-security prompts, against 95% for the restricted one.
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Text extracted automatically; images, tables and formatting may be missing. Original: https://thehackernews.com/2026/08/zoom-annotation-flaws-could-let-meeting.html