# CVE-2026-53275: ipv6: mcast: Fix use-after-free when processing MLD queries

Status: published. Published: 2026-06-25. Updated: 2026-11-10.

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

ipv6: mcast: Fix use-after-free when processing MLD queries

When processing an MLD query, a pointer to the multicast group address
is retrieved when initially parsing the packet. This pointer is later
dereferenced without being reloaded despite the fact that the skb header
might have been reallocated following the pskb_may_pull() calls, leading
to a use-after-free [1].

Fix by copying the multicast group address when the packet is initially
parsed.

[1]
BUG: KASAN: slab-use-after-free in __mld_query_work (net/ipv6/mcast.c:1512)
Read of size 8 at addr ffff8881154b8e90 by task kworker/4:1/118

Workqueue: mld mld_query_work
Call Trace:
<TASK>
dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
print_address_description.constprop.0 (mm/kasan/report.c:378)
print_report (mm/kasan/report.c:482)
kasan_report (mm/kasan/report.c:595)
__mld_query_work (net/ipv6/mcast.c:1512)
mld_query_work (net/ipv6/mcast.c:1563)
process_one_work (kernel/workqueue.c:3314)
worker_thread (kernel/workqueue.c:3397 kernel/workqueue.c:3478)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:158)
ret_from_fork_asm (arch/x86/entry/entry_64.S:245)
</TASK>

[...]

Freed by task 118:
kasan_save_stack (mm/kasan/common.c:57)
kasan_save_track (mm/kasan/common.c:78)
kasan_save_free_info (mm/kasan/generic.c:584)
__kasan_slab_free (mm/kasan/common.c:253 mm/kasan/common.c:285)
kfree (./include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6251 mm/slub.c:6566)
pskb_expand_head (net/core/skbuff.c:2335)
__pskb_pull_tail (net/core/skbuff.c:2878 (discriminator 4))
__mld_query_work (net/ipv6/mcast.c:1495 (discriminator 1))
mld_query_work (net/ipv6/mcast.c:1563)
process_one_work (kernel/workqueue.c:3314)
worker_thread (kernel/workqueue.c:3397 kernel/workqueue.c:3478)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:158)
ret_from_fork_asm (arch/x86/entry/entry_64.S:245)

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 97300b5fdfe28c6edae926926f9467a27cf5889c; < dfaf1f5e7eb81be87582bd6a57d34e61a57d5dea (affected, git); ≥ 97300b5fdfe28c6edae926926f9467a27cf5889c; < 1354271c89d0e5fbf8b3d94097ff0216695209c7 (affected, git); ≥ 97300b5fdfe28c6edae926926f9467a27cf5889c; < 53baa63a4183291574483f89583dbef13677a2c4 (affected, git); ≥ 97300b5fdfe28c6edae926926f9467a27cf5889c; < 2a613bf497029d555a7428406aa8cdb84a503cea (affected, git); ≥ 97300b5fdfe28c6edae926926f9467a27cf5889c; < b2eb8886200b907fc71806869620609f0f4cacb0 (affected, git); ≥ 97300b5fdfe28c6edae926926f9467a27cf5889c; < 4203806f700bb44ea0b05d484d9d40044b47fb04 (affected, git); ≥ 97300b5fdfe28c6edae926926f9467a27cf5889c; < 087dbacf897c020f438f780f0a4a8aa73b6d7c5a (affected, git); ≥ 97300b5fdfe28c6edae926926f9467a27cf5889c; < 791c91dc7a9dfb2457d5e29b8216a6484b9c4b40 (affected, git). Source: CNA: Linux
- Linux / Linux: 2.6.15 (affected); ≥ 0; < 2.6.15 (unaffected, semver); ≥ 5.10.269; ≤ 5.10.* (unaffected, semver); ≥ 5.15.210; ≤ 5.15.* (unaffected, semver); ≥ 6.1.176; ≤ 6.1.* (unaffected, semver); ≥ 6.6.143; ≤ 6.6.* (unaffected, semver); ≥ 6.12.94; ≤ 6.12.* (unaffected, semver); ≥ 6.18.36; ≤ 6.18.* (unaffected, semver); ≥ 7.0.13; ≤ 7.0.* (unaffected, semver); ≥ 7.1; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 TM MFP - GNU/Linux subsystem: ≥ 0; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source: CNA: Linux

- CISA KEV: No listing in collected sources

- EPSS: 0.26% as of 2026-11-09; percentile 18.13%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-416

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/dfaf1f5e7eb81be87582bd6a57d34e61a57d5dea (CNA: Linux)

- https://git.kernel.org/stable/c/1354271c89d0e5fbf8b3d94097ff0216695209c7 (CNA: Linux)

- https://git.kernel.org/stable/c/53baa63a4183291574483f89583dbef13677a2c4 (CNA: Linux)

- https://git.kernel.org/stable/c/2a613bf497029d555a7428406aa8cdb84a503cea (CNA: Linux)

- https://git.kernel.org/stable/c/b2eb8886200b907fc71806869620609f0f4cacb0 (CNA: Linux)

- https://git.kernel.org/stable/c/4203806f700bb44ea0b05d484d9d40044b47fb04 (CNA: Linux)

- https://git.kernel.org/stable/c/087dbacf897c020f438f780f0a4a8aa73b6d7c5a (CNA: Linux)

- https://git.kernel.org/stable/c/791c91dc7a9dfb2457d5e29b8216a6484b9c4b40 (CNA: Linux)

- https://cert-portal.siemens.com/productcert/html/ssa-019113.html (ADP: siemens-SADP)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (ADP: siemens-SADP)

- https://cert-portal.siemens.com/productcert/html/ssa-784472.html (ADP: siemens-SADP)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-53275; retrieved 2026-11-10; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-53275; retrieved 2026-11-10; source updated Not reported

Revision: edbf75b99fd48c0eaddfb751087ec7ebf3418dddba8947a309ef508239f09414

Canonical: https://y2.dev/cve/CVE-2026-53275

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