Skip to content
Fencer Vulns
medium 5.5

CVE-2024-49949 json

net: avoid potential underflow in qdisc_pkt_len_init() with UFO

published 2024-10-21 2 y ago modified 2026-10-15 25 d ago also EUVD-2024-43630

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 20%
public exploits
0
none known

Summary

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

net: avoid potential underflow in qdisc_pkt_len_init() with UFO

After commit 7c6d2ecbda83 ("net: be more gentle about silly gso requests coming from user") virtio_net_hdr_to_skb() had sanity check to detect malicious attempts from user space to cook a bad GSO packet.

Then commit cf9acc90c80ec ("net: virtio_net_hdr_to_skb: count transport header in UFO") while fixing one issue, allowed user space to cook a GSO packet with the following characteristic :

IPv4 SKB_GSO_UDP, gso_size=3, skb->len = 28.

When this packet arrives in qdisc_pkt_len_init(), we end up with hdr_len = 28 (IPv4 header + UDP header), matching skb->len

Then the following sets gso_segs to 0 :

gso_segs = DIV_ROUND_UP(skb->len - hdr_len, shinfo->gso_size);

Then later we set qdisc_skb_cb(skb)->pkt_len to back to zero :/

qdisc_skb_cb(skb)->pkt_len += (gso_segs - 1) * hdr_len;

This leads to the following crash in fq_codel [1]

qdisc_pkt_len_init() is best effort, we only want an estimation of the bytes sent on the wire, not crashing the kernel.

This patch is fixing this particular issue, a following one adds more sanity checks for another potential bug.

[1] [ 70.724101] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 70.724561] #PF: supervisor read access in kernel mode [ 70.724561] #PF: error_code(0x0000) - not-present page [ 70.724561] PGD 10ac61067 P4D 10ac61067 PUD 107ee2067 PMD 0 [ 70.724561] Oops: Oops: 0000 [#1] SMP NOPTI [ 70.724561] CPU: 11 UID: 0 PID: 2163 Comm: b358537762 Not tainted 6.11.0-virtme #991 [ 70.724561] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 70.724561] RIP: 0010:fq_codel_enqueue (net/sched/sch_fq_codel.c:120 net/sched/sch_fq_codel.c:168 net/sched/sch_fq_codel.c:230) sch_fq_codel [ 70.724561] Code: 24 08 49 c1 e1 06 44 89 7c 24 18 45 31 ed 45 31 c0 31 ff 89 44 24 14 4c 03 8b 90 01 00 00 eb 04 39 ca 73 37 4d 8b 39 83 c7 01 <49> 8b 17 49 89 11 41 8b 57 28 45 8b 5f 34 49 c7 07 00 00 00 00 49 All code ======== 0: 24 08 and $0x8,%al 2: 49 c1 e1 06 shl $0x6,%r9 6: 44 89 7c 24 18 mov %r15d,0x18(%rsp) b: 45 31 ed xor %r13d,%r13d e: 45 31 c0 xor %r8d,%r8d 11: 31 ff xor %edi,%edi 13: 89 44 24 14 mov %eax,0x14(%rsp) 17: 4c 03 8b 90 01 00 00 add 0x190(%rbx),%r9 1e: eb 04 jmp 0x24 20: 39 ca cmp %ecx,%edx 22: 73 37 jae 0x5b 24: 4d 8b 39 mov (%r9),%r15 27: 83 c7 01 add $0x1,%edi 2a:* 49 8b 17 mov (%r15),%rdx <-- trapping instruction 2d: 49 89 11 mov %rdx,(%r9) 30: 41 8b 57 28 mov 0x28(%r15),%edx 34: 45 8b 5f 34 mov 0x34(%r15),%r11d 38: 49 c7 07 00 00 00 00 movq $0x0,(%r15) 3f: 49 rex.WB

Code starting with the faulting instruction =========================================== 0: 49 8b 17 mov (%r15),%rdx 3: 49 89 11 mov %rdx,(%r9) 6: 41 8b 57 28 mov 0x28(%r15),%edx a: 45 8b 5f 34 mov 0x34(%r15),%r11d e: 49 c7 07 00 00 00 00 movq $0x0,(%r15) 15: 49 rex.WB [ 70.724561] RSP: 0018:ffff95ae85e6fb90 EFLAGS: 00000202 [ 70.724561] RAX: 0000000002000000 RBX: ffff95ae841de000 RCX: 0000000000000000 [ 70.724561] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001 [ 70.724561] RBP: ffff95ae85e6fbf8 R08: 0000000000000000 R09: ffff95b710a30000 [ 70.724561] R10: 0000000000000000 R11: bdf289445ce31881 R12: ffff95ae85e6fc58 [ 70.724561] R13: 0000000000000000 R14: 0000000000000040 R15: 0000000000000000 [ 70.724561] FS: 000000002c5c1380(0000) GS:ffff95bd7fcc0000(0000) knlGS:0000000000000000 [ 70.724561] CS: 0010 DS: 0000 ES: 0000 C ---truncated---

Patch / fix

  • Linux Linux 4.15, 4.19.323, 5.4.285, 5.10.227, 5.15.168, 6.1.113, 6.6.55, 6.10.14, 6.11.3, 6.12
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem V1.1.1
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens RUGGEDCOM RST2428P V3.2
  • Siemens SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family V3.2
  • Siemens SCALANCE XCM-/XRM-/XCH-/XRH-300 family V3.2
  • linux Debian 12 6.1.115-1
  • linux Debian 14, Debian 13 6.11.4-1

debian advisories DEBIAN-CVE-2024-49949

  • linux Ubuntu 20.04 LTS 5.4.0-208.228
  • linux Ubuntu 22.04 LTS 5.15.0-127.137
  • linux Ubuntu 24.04 LTS 6.8.0-54.56
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1140.150
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1073.79
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1023.25
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1143.152
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1072.80

ubuntu advisories UBUNTU-CVE-2024-49949

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

  • kernel RHEL 8 4.18.0-553.32.1.el8_10
  • perf RHEL 8 4.18.0-553.32.1.el8_10
  • bpftool RHEL 8 4.18.0-553.32.1.el8_10
  • kernel-core RHEL 8 4.18.0-553.32.1.el8_10
  • kernel-tools RHEL 8 4.18.0-553.32.1.el8_10
  • python3-perf RHEL 8 4.18.0-553.32.1.el8_10
  • kernel-modules RHEL 8 4.18.0-553.32.1.el8_10
  • kernel-zfcpdump RHEL 8 4.18.0-553.32.1.el8_10

red hat advisories RHSA-2025:2270RHSA-2024:10943RHSA-2024:10944RHSA-2024:10939

  • kernel-source Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1
  • kernel-default Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1
  • kernel-kvmsmall Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1
  • kernel-default-base Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1.21.4
  • kernel-livepatch-MICRO-6-0_Update_4 Linux Micro 6.1, Linux Micro 6.0 1-1.2
  • kernel-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-22.1
  • kernel-source-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-22.1
  • kernel-livepatch-MICRO-6-0-RT_Update_4 Linux Micro 6.1, Linux Micro 6.0 1-1.1

suse advisories SUSE-SU-2025:20164-1SUSE-SU-2025:20247-1SUSE-SU-2025:20163-1SUSE-SU-2025:20246-1SUSE-SU-2025:0034-1SUSE-SU-2024:4387-1

  • kernel-source-longterm openSUSE Tumbleweed 6.12.11-1.1
  • kernel-source openSUSE Tumbleweed 6.11.8-1.1

opensuse advisories openSUSE-SU-2025:14705-1openSUSE-SU-2024:14500-1

  • kernel AlmaLinux 9 5.14.0-503.16.1.el9_5
  • rv AlmaLinux 9 5.14.0-503.16.1.el9_5
  • perf AlmaLinux 9 5.14.0-503.16.1.el9_5
  • rtla AlmaLinux 9 5.14.0-503.16.1.el9_5
  • bpftool AlmaLinux 9 7.4.0-503.16.1.el9_5
  • libperf AlmaLinux 9 5.14.0-503.16.1.el9_5
  • kernel-rt AlmaLinux 9 5.14.0-503.16.1.el9_5
  • kernel-64k AlmaLinux 9 5.14.0-503.16.1.el9_5

almalinux advisories ALSA-2024:10939ALSA-2024:10943ALSA-2024:10944

  • kernel-rt Rocky Linux 8 4.18.0-553.32.1.rt7.373.el8_10
  • kernel Rocky Linux 8 4.18.0-553.32.1.el8_10

rocky linux advisories RLSA-2024:10944RLSA-2024:10943

  • kernel CBL-Mariner 2.0 5.15.173.1-1

azure linux advisories AZL-52628

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2024-49949 updated cvss 5.5

kernel: net: avoid potential underflow in qdisc_pkt_len_init() with UFO

  • 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
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat CodeReady Linux Builder (v. 9) libperf 5.14.0-503.16.1.el9_5, kernel-debuginfo-common-s390x 5.14.0-503.16.1.el9_5, kernel-debuginfo-common-x86_64 5.14.0-503.16.1.el9_5, kernel-debuginfo-common-aarch64 5.14.0-503.16.1.el9_5, kernel-debuginfo-common-ppc64le 5.14.0-503.16.1.el9_5
    fixed: vendor fix RHSA-2024:10939
  • Red Hat CodeReady Linux Builder EUS (v.9.4) libperf 5.14.0-427.57.1.el9_4, kernel-debuginfo-common-s390x 5.14.0-427.57.1.el9_4, kernel-debuginfo-common-x86_64 5.14.0-427.57.1.el9_4, kernel-debuginfo-common-aarch64 5.14.0-427.57.1.el9_4, kernel-debuginfo-common-ppc64le 5.14.0-427.57.1.el9_4
    fixed: vendor fix RHSA-2025:2270
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-503.16.1.el9_5, perf 5.14.0-503.16.1.el9_5, rtla 5.14.0-503.16.1.el9_5, kernel-devel-matched 5.14.0-503.16.1.el9_5, kernel-64k-devel-matched 5.14.0-503.16.1.el9_5, kernel-debug-devel-matched 5.14.0-503.16.1.el9_5, +6 more
    fixed: vendor fix RHSA-2024:10939
  • Red Hat Enterprise Linux AppStream EUS (v.9.4) rv 5.14.0-427.57.1.el9_4, perf 5.14.0-427.57.1.el9_4, rtla 5.14.0-427.57.1.el9_4, kernel-devel-matched 5.14.0-427.57.1.el9_4, kernel-64k-devel-matched 5.14.0-427.57.1.el9_4, kernel-debug-devel-matched 5.14.0-427.57.1.el9_4, +6 more
    fixed: vendor fix RHSA-2025:2270
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.32.1.el8_10, kernel 4.18.0-553.32.1.el8_10, bpftool 4.18.0-553.32.1.el8_10, kernel-core 4.18.0-553.32.1.el8_10, kernel-tools 4.18.0-553.32.1.el8_10, python3-perf 4.18.0-553.32.1.el8_10, +15 more
    fixed: vendor fix RHSA-2024:10943
  • Red Hat Enterprise Linux BaseOS (v. 9) bpftool 7.4.0-503.16.1.el9_5, kernel 5.14.0-503.16.1.el9_5, kernel-64k 5.14.0-503.16.1.el9_5, kernel-core 5.14.0-503.16.1.el9_5, kernel-tools 5.14.0-503.16.1.el9_5, python3-perf 5.14.0-503.16.1.el9_5, +29 more
    fixed: vendor fix RHSA-2024:10939
  • Red Hat Enterprise Linux BaseOS EUS (v.9.4) bpftool 7.3.0-427.57.1.el9_4, kernel 5.14.0-427.57.1.el9_4, kernel-64k 5.14.0-427.57.1.el9_4, kernel-core 5.14.0-427.57.1.el9_4, kernel-tools 5.14.0-427.57.1.el9_4, python3-perf 5.14.0-427.57.1.el9_4, +28 more
    fixed: vendor fix RHSA-2025:2270
show 7 more
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.32.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.32.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.32.1.el8_10
    fixed: vendor fix RHSA-2024:10943
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.32.1.rt7.373.el8_10, kernel-rt-kvm 4.18.0-553.32.1.rt7.373.el8_10, kernel-rt-core 4.18.0-553.32.1.rt7.373.el8_10, kernel-rt-modules 4.18.0-553.32.1.rt7.373.el8_10, kernel-rt-debug-kvm 4.18.0-553.32.1.rt7.373.el8_10, kernel-rt-debug-core 4.18.0-553.32.1.rt7.373.el8_10, +4 more
    fixed: vendor fix RHSA-2024:10944
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-503.16.1.el9_5, kernel-rt-core 5.14.0-503.16.1.el9_5, kernel-rt-modules 5.14.0-503.16.1.el9_5, kernel-rt-debug-core 5.14.0-503.16.1.el9_5, kernel-rt-modules-core 5.14.0-503.16.1.el9_5, kernel-rt-debug-modules 5.14.0-503.16.1.el9_5, +4 more
    fixed: vendor fix RHSA-2024:10939
  • Red Hat Enterprise Linux Real Time EUS (v.9.4) kernel-rt 5.14.0-427.57.1.el9_4, kernel-rt-core 5.14.0-427.57.1.el9_4, kernel-rt-modules 5.14.0-427.57.1.el9_4, kernel-rt-debug-core 5.14.0-427.57.1.el9_4, kernel-rt-modules-core 5.14.0-427.57.1.el9_4, kernel-rt-debug-modules 5.14.0-427.57.1.el9_4, +4 more
    fixed: vendor fix RHSA-2025:2270
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-503.16.1.el9_5, kernel-rt-kvm 5.14.0-503.16.1.el9_5, kernel-rt-core 5.14.0-503.16.1.el9_5, kernel-rt-modules 5.14.0-503.16.1.el9_5, kernel-rt-debug-kvm 5.14.0-503.16.1.el9_5, kernel-rt-debug-core 5.14.0-503.16.1.el9_5, +6 more
    fixed: vendor fix RHSA-2024:10939
  • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.4) kernel-rt 5.14.0-427.57.1.el9_4, kernel-rt-kvm 5.14.0-427.57.1.el9_4, kernel-rt-core 5.14.0-427.57.1.el9_4, kernel-rt-modules 5.14.0-427.57.1.el9_4, kernel-rt-debug-kvm 5.14.0-427.57.1.el9_4, kernel-rt-debug-core 5.14.0-427.57.1.el9_4, +6 more
    fixed: vendor fix RHSA-2025:2270
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.32.1.rt7.373.el8_10, kernel-rt-core 4.18.0-553.32.1.rt7.373.el8_10, kernel-rt-modules 4.18.0-553.32.1.rt7.373.el8_10, kernel-rt-debug-core 4.18.0-553.32.1.rt7.373.el8_10, kernel-rt-debug-modules 4.18.0-553.32.1.rt7.373.el8_10, kernel-rt-modules-extra 4.18.0-553.32.1.rt7.373.el8_10, +2 more
    fixed: vendor fix RHSA-2024:10944

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 ICSA-24-102-01 updated cvss 5.5

Siemens SIMATIC S7-1500 TM MFP

  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

cisa ICSA-25-226-07 updated cvss 5.5

Siemens Third-Party Components in SINEC OS

  • Siemens RUGGEDCOM RST2428P (6GK6242-6PA00) < 3.2
    affected: fixed in V3.2 support.industry.siemens.com
  • Siemens SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family < 3.2
    affected: fixed in V3.2
  • Siemens SCALANCE XCM-/XRM-/XCH-/XRH-300 family < 3.2
    affected: fixed in V3.2 support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

cisa ICSA-23-348-10 updated cvss 5.5

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 y ago

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 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
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens RUGGEDCOM RST2428P
  • Siemens SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family
  • Siemens SCALANCE XCM-/XRM-/XCH-/XRH-300 family

Classification

Weakness
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.