CVE-2021-45707
Out-of-bounds Write in nix
An issue was discovered in the nix crate 0.16.0 and later before 0.20.2, 0.21.x before 0.21.2, and 0.22.x before 0.22.2 for Rust. unistd::getgrouplist has an out-of-bounds write if a user is in more than 16 /etc/groups groups.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
An issue was discovered in the nix crate 0.16.0 and later before 0.20.2, 0.21.x before 0.21.2, and 0.22.x before 0.22.2 for Rust. unistd::getgrouplist has an out-of-bounds write if a user is in more than 16 /etc/groups groups.
- Record
CVE-2021-45707- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 7.5 High
AV:N/AC:L/Au:N/C:P/I:P/A:P - Weakness
- CWE-787
- Updated
- 2026-11-02
CVE ListNo score
An issue was discovered in the nix crate 0.16.0 and later before 0.20.2, 0.21.x before 0.21.2, and 0.22.x before 0.22.2 for Rust. unistd::getgrouplist has an out-of-bounds write if a user is in more than 16 /etc/groups groups.
- Record
CVE-2021-45707- Updated
- 2026-11-02
EUVDEUVD-2022-0497No score
An issue was discovered in the nix crate 0.16.0 and later before 0.20.2, 0.21.x before 0.21.2, and 0.22.x before 0.22.2 for Rust. unistd::getgrouplist has an out-of-bounds write if a user is in more than 16 /etc/groups groups.
- Record
EUVD-2022-0497- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-76w9-p8mg-j927
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.
- Record
GHSA-76w9-p8mg-j927- CVSS 3.1
- 6.7 Medium
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
GitHub AdvisoriesGHSA-wgrg-5h56-jg27No score
Out-of-bounds write in nix::unistd::getgrouplist
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 reqested 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.
- Record
GHSA-wgrg-5h56-jg27- Updated
- 2026-11-02
OSV
An issue was discovered in the nix crate 0.16.0 and later before 0.20.2, 0.21.x before 0.21.2, and 0.22.x before 0.22.2 for Rust. unistd::getgrouplist has an out-of-bounds write if a user is in more than 16 /etc/groups groups.
- Record
CVE-2021-45707- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
Show 5 moreShow less
OSVDEBIAN-CVE-2021-45707
An issue was discovered in the nix crate 0.16.0 and later before 0.20.2, 0.21.x before 0.21.2, and 0.22.x before 0.22.2 for Rust. unistd::getgrouplist has an out-of-bounds write if a user is in more than 16 /etc/groups groups.
- Record
DEBIAN-CVE-2021-45707- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVGHSA-76w9-p8mg-j927
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.
- Record
GHSA-76w9-p8mg-j927- CVSS 3.1
- 6.7 Medium
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
OSVUBUNTU-CVE-2021-45707
An issue was discovered in the nix crate 0.16.0 and later before 0.20.2, 0.21.x before 0.21.2, and 0.22.x before 0.22.2 for Rust. unistd::getgrouplist has an out-of-bounds write if a user is in more than 16 /etc/groups groups.
- Record
UBUNTU-CVE-2021-45707- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVGHSA-wgrg-5h56-jg27No score
Out-of-bounds write in nix::unistd::getgrouplist
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 reqested 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.
- Record
GHSA-wgrg-5h56-jg27- Updated
- 2026-11-02
OSVRUSTSEC-2021-0119No score
Out-of-bounds write in nix::unistd::getgrouplist
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.
- Record
RUSTSEC-2021-0119- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
nixcrates.io | 0.21.0 up to 0.21.2 | 0.21.2 |
nixcrates.io | 0.22.0 up to 0.22.2 | 0.22.2 |
nixcrates.io | 0.16.0 up to 0.20.2 | 0.20.2 |
rust-nixDebian:12 | before 0.23.0-1 | 0.23.0-1 |
rust-nixDebian:13 | before 0.23.0-1 | 0.23.0-1 |
rust-nixDebian:14 | before 0.23.0-1 | 0.23.0-1 |
nixcrates.io | 0.16.0 up to 0.20.2, 0.21.0-0 up to 0.21.2, 0.22.0-0 up to 0.22.2, 0.23.0-0 up to 0.23.0 | 0.20.20.21.20.22.20.23.0 |
rust-nixUbuntu:20.04:LTS | All versions, plus listed versions 0.14.1-10.15.0-10.15.0-20.16.1-1 | None known |
rust-nixUbuntu:22.04:LTS | All versions, plus listed versions 0.19.0-10.19.0-20.23.1-1 | None known |
rust-nixUbuntu:24.04:LTS | All versions, plus listed versions 0.26.2-10.27.1-10.27.1-1build1 | None known |
rust-nixUbuntu:25.10 | All versions, plus listed versions 0.29.0-2 | None known |
rust-nixUbuntu:26.10 | All versions, plus listed versions 0.30.1-3 | None known |
rust-nixUbuntu:26.04:LTS | All versions, plus listed versions 0.29.0-20.30.1-3 | None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-45707 is a critical vulnerability (CVSS 9.8) in Nix Project Nix, published September 27, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.69%, the 77th percentile. Fixed in nix 0.21.2.