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Security Advisories: GSA_kwCzR0hTQS03Nnc5LXA4bWctajkyN80fiA

Out-of-bounds Write in nix

On certain platforms, if a user has more than 16 groups, the nix::unistd::getgrouplist function will call the libc getgrouplist function with a length parameter greater than the size of the buffer it provides, resulting in an out-of-bounds write and memory corruption.

The libc getgrouplist function takes an in/out parameter ngroups specifying the size of the group buffer. When the buffer is too small to hold all of the requested user's group memberships, some libc implementations, including glibc and Solaris libc, will modify ngroups to indicate the actual number of groups for the user, in addition to returning an error. The version of nix::unistd::getgrouplist in nix 0.16.0 and up will resize the buffer to twice its size, but will not read or modify the ngroups variable. Thus, if the user has more than twice as many groups as the initial buffer size of 8, the next call to getgrouplist will then write past the end of the buffer.

The issue would require editing /etc/groups to exploit, which is usually only editable by the root user.

Permalink: https://github.com/advisories/GHSA-76w9-p8mg-j927
JSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS03Nnc5LXA4bWctajkyN80fiA
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Moderate
Classification: General
Published: over 2 years ago
Updated: 2 months ago

CVSS Score: 6.7
CVSS vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Identifiers: GHSA-76w9-p8mg-j927, CVE-2021-45707
References:

• https://nvd.nist.gov/vuln/detail/CVE-2021-45707
• https://raw.githubusercontent.com/rustsec/advisory-db/main/crates/nix/RUSTSEC-2021-0119.md
• https://rustsec.org/advisories/RUSTSEC-2021-0119.html
• https://github.com/advisories/GHSA-wgrg-5h56-jg27
• https://github.com/nix-rust/nix/issues/1541
• https://github.com/advisories/GHSA-76w9-p8mg-j927

Repository: https://github.com/nix-rust/nix
Blast Radius: 29.2

Affected Packages