net: fix udp gso skb_segment after pull from frag_list

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Summary

CVECVE-2025-38124
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-07-03 09:15:26 UTC
Updated2026-05-12 13:16:43 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net: fix udp gso skb_segment after pull from frag_list Commit a1e40ac5b5e9 ("net: gso: fix udp gso fraglist segmentation after pull from frag_list") detected invalid geometry in frag_list skbs and redirects them from skb_segment_list to more robust skb_segment. But some packets with modified geometry can also hit bugs in that code. We don't know how many such cases exist. Addressing each one by one also requires touching the complex skb_segment code, which risks introducing bugs for other types of skbs. Instead, linearize all these packets that fail the basic invariants on gso fraglist skbs. That is more robust. If only part of the fraglist payload is pulled into head_skb, it will always cause exception when splitting skbs by skb_segment. For detailed call stack information, see below. Valid SKB_GSO_FRAGLIST skbs - consist of two or more segments - the head_skb holds the protocol headers plus first gso_size - one or more frag_list skbs hold exactly one segment - all but the last must be gso_size Optional datapath hooks such as NAT and BPF (bpf_skb_pull_data) can modify fraglist skbs, breaking these invariants. In extreme cases they pull one part of data into skb linear. For UDP, this causes three payloads with lengths of (11,11,10) bytes were pulled tail to become (12,10,10) bytes. The skbs no longer meets the above SKB_GSO_FRAGLIST conditions because payload was pulled into head_skb, it needs to be linearized before pass to regular skb_segment. skb_segment+0xcd0/0xd14 __udp_gso_segment+0x334/0x5f4 udp4_ufo_fragment+0x118/0x15c inet_gso_segment+0x164/0x338 skb_mac_gso_segment+0xc4/0x13c __skb_gso_segment+0xc4/0x124 validate_xmit_skb+0x9c/0x2c0 validate_xmit_skb_list+0x4c/0x80 sch_direct_xmit+0x70/0x404 __dev_queue_xmit+0x64c/0xe5c neigh_resolve_output+0x178/0x1c4 ip_finish_output2+0x37c/0x47c __ip_finish_output+0x194/0x240 ip_finish_output+0x20/0xf4 ip_output+0x100/0x1a0 NF_HOOK+0xc4/0x16c ip_forward+0x314/0x32c ip_rcv+0x90/0x118 __netif_receive_skb+0x74/0x124 process_backlog+0xe8/0x1a4 __napi_poll+0x5c/0x1f8 net_rx_action+0x154/0x314 handle_softirqs+0x154/0x4b8 [118.376811] [C201134] rxq0_pus: [name:bug&]kernel BUG at net/core/skbuff.c:4278! [118.376829] [C201134] rxq0_pus: [name:traps&]Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP [118.470774] [C201134] rxq0_pus: [name:mrdump&]Kernel Offset: 0x178cc00000 from 0xffffffc008000000 [118.470810] [C201134] rxq0_pus: [name:mrdump&]PHYS_OFFSET: 0x40000000 [118.470827] [C201134] rxq0_pus: [name:mrdump&]pstate: 60400005 (nZCv daif +PAN -UAO) [118.470848] [C201134] rxq0_pus: [name:mrdump&]pc : [0xffffffd79598aefc] skb_segment+0xcd0/0xd14 [118.470900] [C201134] rxq0_pus: [name:mrdump&]lr : [0xffffffd79598a5e8] skb_segment+0x3bc/0xd14 [118.470928] [C201134] rxq0_pus: [name:mrdump&]sp : ffffffc008013770

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

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

Problem Types: CWE-401

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 080e6c9a3908de193a48f646c5ce1bfb15676ffc 0e65f38bd1aa14ea86e221b7bb814d38278d86c3 git Not specified
CNA Linux Linux affected af3122f5fdc0d00581d6e598a668df6bf54c9daa 85eef1748c024da1a191aed56b30a3a65958c50c git Not specified
CNA Linux Linux affected a1e40ac5b5e9077fe1f7ae0eb88034db0f9ae1ab 4399f59a9467a324ed46657555f0e1f209a14acb git Not specified
CNA Linux Linux affected a1e40ac5b5e9077fe1f7ae0eb88034db0f9ae1ab a04302867094bdc6efac1b598370fc47cf3f2388 git Not specified
CNA Linux Linux affected a1e40ac5b5e9077fe1f7ae0eb88034db0f9ae1ab 3382a1ed7f778db841063f5d7e317ac55f9e7f72 git Not specified
CNA Linux Linux affected 33e28acf42ee863f332a958bfc2f1a284a3659df git Not specified
CNA Linux Linux affected 3cd00d2e3655fad3bda96dc1ebf17b6495f86fea git Not specified
CNA Linux Linux affected 6.12 Not specified
CNA Linux Linux unaffected 6.12 semver Not specified
CNA Linux Linux unaffected 6.1.142 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.94 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.34 6.12.* semver Not specified
CNA Linux Linux unaffected 6.15.3 6.15.* semver Not specified
CNA Linux Linux unaffected 6.16 * original_commit_for_fix Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified

References

ReferenceSourceLinkTags
lists.debian.org/debian-lts-announce/2025/10/msg00008.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org Third Party Advisory
git.kernel.org/stable/c/a04302867094bdc6efac1b598370fc47cf3f2388 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-082556.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/0e65f38bd1aa14ea86e221b7bb814d38278d86c3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/4399f59a9467a324ed46657555f0e1f209a14acb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/3382a1ed7f778db841063f5d7e317ac55f9e7f72 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/85eef1748c024da1a191aed56b30a3a65958c50c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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