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Fencer Vulns
high 7.5

CVE-2025-22059 json

udp: Fix multiple wraparounds of sk->sk_rmem_alloc.

published 2025-04-16 18 mo ago modified 2026-08-05 3 mo ago also EUVD-2025-11237

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

udp: Fix multiple wraparounds of sk->sk_rmem_alloc.

__udp_enqueue_schedule_skb() has the following condition:

if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) goto drop;

sk->sk_rcvbuf is initialised by net.core.rmem_default and later can be configured by SO_RCVBUF, which is limited by net.core.rmem_max, or SO_RCVBUFFORCE.

If we set INT_MAX to sk->sk_rcvbuf, the condition is always false as sk->sk_rmem_alloc is also signed int.

Then, the size of the incoming skb is added to sk->sk_rmem_alloc unconditionally.

This results in integer overflow (possibly multiple times) on sk->sk_rmem_alloc and allows a single socket to have skb up to net.core.udp_mem[1].

For example, if we set a large value to udp_mem[1] and INT_MAX to sk->sk_rcvbuf and flood packets to the socket, we can see multiple overflows:

# cat /proc/net/sockstat | grep UDP: UDP: inuse 3 mem 7956736 <-- (7956736 << 12) bytes > INT_MAX * 15 ^- PAGE_SHIFT # ss -uam State Recv-Q ... UNCONN -1757018048 ... <-- flipping the sign repeatedly skmem:(r2537949248,rb2147483646,t0,tb212992,f1984,w0,o0,bl0,d0)

Previously, we had a boundary check for INT_MAX, which was removed by commit 6a1f12dd85a8 ("udp: relax atomic operation on sk->sk_rmem_alloc").

A complete fix would be to revert it and cap the right operand by INT_MAX:

rmem = atomic_add_return(size, &sk->sk_rmem_alloc); if (rmem > min(size + (unsigned int)sk->sk_rcvbuf, INT_MAX)) goto uncharge_drop;

but we do not want to add the expensive atomic_add_return() back just for the corner case.

Casting rmem to unsigned int prevents multiple wraparounds, but we still allow a single wraparound.

# cat /proc/net/sockstat | grep UDP: UDP: inuse 3 mem 524288 <-- (INT_MAX + 1) >> 12

# ss -uam State Recv-Q ... UNCONN -2147482816 ... <-- INT_MAX + 831 bytes skmem:(r2147484480,rb2147483646,t0,tb212992,f3264,w0,o0,bl0,d14468947)

So, let's define rmem and rcvbuf as unsigned int and check skb->truesize only when rcvbuf is large enough to lower the overflow possibility.

Note that we still have a small chance to see overflow if multiple skbs to the same socket are processed on different core at the same time and each size does not exceed the limit but the total size does.

Note also that we must ignore skb->truesize for a small buffer as explained in commit 363dc73acacb ("udp: be less conservative with sock rmem accounting").

Patch / fix

  • Linux Linux 6.12.23, 6.13.11, 6.14.2, 6.15
  • linux Debian 14, Debian 13 6.12.25-1

debian advisories DEBIAN-CVE-2025-22059

  • linux-gcp-6.11 Ubuntu 24.04 LTS 6.11.0-1016.16~24.04.1
  • linux-hwe-6.11 Ubuntu 24.04 LTS 6.11.0-28.28~24.04.1
  • linux-oem-6.11 Ubuntu 24.04 LTS 6.11.0-1024.24
  • linux-azure-6.11 Ubuntu 24.04 LTS 6.11.0-1018.18~24.04.1
  • linux-nvidia-6.11 Ubuntu 24.04 LTS 6.11.0-1012.12
  • linux-lowlatency-hwe-6.11 Ubuntu 24.04 LTS 6.11.0-1015.16~24.04.2

ubuntu advisories UBUNTU-CVE-2025-22059

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-22059 updated cvss 5.7

kernel: udp: Fix multiple wraparounds of sk->sk_rmem_alloc.

  • Red Hat Enterprise Linux 10 kernel
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
13 mo ago

Exploit prediction

0.48% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA ADP 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-190 Integer Overflow or Wraparound
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.