CVE-2024-26924

netfilter: nft_set_pipapo: do not free live element

Published Apr 24, 2024 CVSS 3.1 · 7.8 High EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

netfilter: nft_set_pipapo: do not free live element

Pablo reports a crash with large batches of elements with a
back-to-back add/remove pattern. Quoting Pablo:

add_elem("00000000") timeout 100 ms
...
add_elem("0000000X") timeout 100 ms
del_elem("0000000X") <---------------- delete one that was just added
...
add_elem("00005000") timeout 100 ms

1) nft_pipapo_remove() removes element 0000000X
Then, KASAN shows a splat.

Looking at the remove function there is a chance that we will drop a
rule that maps to a non-deactivated element.

Removal happens in two steps, first we do a lookup for key k and return the
to-be-removed element and mark it as inactive in the next generation.
Then, in a second step, the element gets removed from the set/map.

The _remove function does not work correctly if we have more than one
element that share the same key.

This can happen if we insert an element into a set when the set already
holds an element with same key, but the element mapping to the existing
key has timed out or is not active in the next generation.

In such case its possible that removal will unmap the wrong element.
If this happens, we will leak the non-deactivated element, it becomes
unreachable.

The element that got deactivated (and will be freed later) will
remain reachable in the set data structure, this can result in
a crash when such an element is retrieved during lookup (stale
pointer).

Add a check that the fully matching key does in fact map to the element
that we have marked as inactive in the deactivation step.
If not, we need to continue searching.

Add a bug/warn trap at the end of the function as well, the remove
function must not ever be called with an invisible/unreachable/non-existent
element.

v2: avoid uneeded temporary variable (Stefano)

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-3842-1 linux-5.10 security update
Debian DSA Debian DSA DSA-5680-1 linux security update
Debian DSA Debian DSA DSA-5681-1 linux security update
Ubuntu USN Ubuntu USN USN-6863-1 Linux kernel vulnerability
Ubuntu USN Ubuntu USN USN-6864-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6864-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6864-3 Linux kernel (GKE) vulnerabilities
Ubuntu USN Ubuntu USN USN-6869-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6870-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6870-2 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-6871-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-6872-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6872-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6873-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6873-2 Linux kernel (StarFive) vulnerabilities
Ubuntu USN Ubuntu USN USN-6874-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-6875-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-6892-1 Linux kernel (IBM) vulnerabilities
Ubuntu USN Ubuntu USN USN-6900-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6918-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6919-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6927-1 Linux kernel vulnerabilities
History
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Metrics epss

{'score': 0.00088}

epss

{'score': 0.00089}

Type Values Removed Values Added
First Time appeared Debian
Debian debian Linux
CPEs cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.9:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.9:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.9:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.9:rc4:*:*:*:*:*:*
Vendors & Products Debian
Debian debian Linux
Type Values Removed Values Added
First Time appeared Redhat rhel Eus
CPEs cpe:/a:redhat:rhel_eus:9.4
Vendors & Products Redhat rhel Eus
Type Values Removed Values Added
CPEs cpe:/a:redhat:enterprise_linux:9
cpe:/o:redhat:enterprise_linux:9
Type Values Removed Values Added
First Time appeared Redhat
Redhat enterprise Linux
CPEs cpe:/a:redhat:enterprise_linux:8::nfv
cpe:/o:redhat:enterprise_linux:8
Vendors & Products Redhat
Redhat enterprise Linux
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Aug 5, 2026, 11:28 AM
Reserved
Feb 19, 2024, 2:20 PM
Status
Modified
Published
Apr 25, 2024, 6:15 AM
Modified
Aug 4, 2026, 11:17 AM
Severity
Low
Public date
Apr 24, 2024, 12:00 AM