What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-10-04 · updated 2026-06-17
• Weakness: CWE-190

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.

Affected products

• Debian Linux: 9.0
• NetApp Management Services For Element Software And Netapp Hci: all versions
• redis hiredis: before 1.0.1 — fixed in 1.0.1

How to fix

Upgrade to a fixed version: redis hiredis 1.0.1. Check the vendor advisory for mitigations.

References

• https://github.com/redis/hiredis/commit/76a7b10005c70babee357a7d0f2becf28ec7ed1e
• https://github.com/redis/hiredis/security/advisories/GHSA-hfm9-39pp-55p2
• https://lists.debian.org/debian-lts-announce/2021/10/msg00007.html
• https://security.gentoo.org/glsa/202210-32
• https://security.netapp.com/advisory/ntap-20211104-0003/
• 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://github.com/redis/hiredis/commit/76a7b10005c70babee357a7d0f2becf28ec7ed1e
• https://github.com/redis/hiredis/security/advisories/GHSA-hfm9-39pp-55p2
• https://lists.debian.org/debian-lts-announce/2021/10/msg00007.html
• https://security.gentoo.org/glsa/202210-32
• https://security.netapp.com/advisory/ntap-20211104-0003/
• 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

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