# CVE-2016-9436: Tats w3m uninitialized value in parsetagx.c

Source: https://junglewise.ai/threats/cve-2016-9436-tats-w3m-uninitialized-value-in-parsetagx-c  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2017-01-20. Updated: 2026-05-13  
License: CC BY 4.0 with a link back

CVE-2016-9436 · Severity: medium · CVSS 6.5 · Published 2017-01-20

w3m is a text-based web browser used to view websites in a terminal environment. A vulnerability exists where the browser fails to properly handle certain HTML tags, such as the italics tag. An attacker could use a specially crafted web page to cause the browser to crash, resulting in a denial of service for the user.

Technologies: [Opensuse Leap](https://junglewise.ai/threats/technologies/leap). Vendors: [Opensuse](https://junglewise.ai/threats/vendors/opensuse).

## Quick answers

**Is CVE-2016-9436 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-9436 being exploited in the wild.

**How severe is CVE-2016-9436?** Medium severity, with a CVSS score of 6.5, published 20 January 2017.

**Which products and versions are affected?** tats w3m before 0.5.3+git20161009.

**Is there a fix for CVE-2016-9436?** A patch was published on 2016-10-09: Fix committed to w3m repository Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2016-9436 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2016-9436?** Check whether you run Opensuse Leap or Tats W3m. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in the `parse_tag` function within `parsetagx.c` of w3m due to the use of uninitialized values. Specifically, the application fails to properly initialize the `tagname` buffer or associated state when encountering certain HTML tags, such as the `<i>` tag. A remote attacker can exploit this by providing a maliciously crafted HTML file that triggers a conditional jump or move based on these uninitialized values, leading to an application crash (Denial of Service). The issue was identified using Valgrind and AFL-fuzz and is addressed by ensuring proper initialization (e.g., setting `tagname[0] = '\0'`) in the parser. This was patched in the git commit 33509cc81ec5f2ba44eb6fd98bd5c1b5873e46bd.

## Affected products

- tats w3m before 0.5.3+git20161009

## Timeline

- 2016-08-17: disclosed: Issue reported on GitHub by user kcwu
- 2016-10-09: patched: Fix committed to w3m repository
- 2017-01-20: advisory: NVD publication date

## References

- [http://lists.opensuse.org/opensuse-updates/2016-12/msg00084.html](http://lists.opensuse.org/opensuse-updates/2016-12/msg00084.html)
- [http://www.openwall.com/lists/oss-security/2016/11/18/3](http://www.openwall.com/lists/oss-security/2016/11/18/3)
- [http://www.securityfocus.com/bid/94407](http://www.securityfocus.com/bid/94407)
- [https://github.com/tats/w3m/commit/33509cc81ec5f2ba44eb6fd98bd5c1b5873e46bd](https://github.com/tats/w3m/commit/33509cc81ec5f2ba44eb6fd98bd5c1b5873e46bd)
- [https://github.com/tats/w3m/issues/16](https://github.com/tats/w3m/issues/16)
- [https://security.gentoo.org/glsa/201701-08](https://security.gentoo.org/glsa/201701-08)

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