# CVE-2026-31546: net: bonding: fix NULL deref in bond_debug_rlb_hash_show

Status: published. Published: 2026-04-24. Updated: 2026-11-05.

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

net: bonding: fix NULL deref in bond_debug_rlb_hash_show

rlb_clear_slave intentionally keeps RLB hash-table entries on
the rx_hashtbl_used_head list with slave set to NULL when no
replacement slave is available. However, bond_debug_rlb_hash_show
visites client_info->slave without checking if it's NULL.

Other used-list iterators in bond_alb.c already handle this NULL-slave
state safely:

- rlb_update_client returns early on !client_info->slave
- rlb_req_update_slave_clients, rlb_clear_slave, and rlb_rebalance
compare slave values before visiting
- lb_req_update_subnet_clients continues if slave is NULL

The following NULL deref crash can be trigger in
bond_debug_rlb_hash_show:

[    1.289791] BUG: kernel NULL pointer dereference, address: 0000000000000000
[    1.292058] RIP: 0010:bond_debug_rlb_hash_show (drivers/net/bonding/bond_debugfs.c:41)
[    1.293101] RSP: 0018:ffffc900004a7d00 EFLAGS: 00010286
[    1.293333] RAX: 0000000000000000 RBX: ffff888102b48200 RCX: ffff888102b48204
[    1.293631] RDX: ffff888102b48200 RSI: ffffffff839daad5 RDI: ffff888102815078
[    1.293924] RBP: ffff888102815078 R08: ffff888102b4820e R09: 0000000000000000
[    1.294267] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888100f929c0
[    1.294564] R13: ffff888100f92a00 R14: 0000000000000001 R15: ffffc900004a7ed8
[    1.294864] FS:  0000000001395380(0000) GS:ffff888196e75000(0000) knlGS:0000000000000000
[    1.295239] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    1.295480] CR2: 0000000000000000 CR3: 0000000102adc004 CR4: 0000000000772ef0
[    1.295897] Call Trace:
[    1.296134]  seq_read_iter (fs/seq_file.c:231)
[    1.296341]  seq_read (fs/seq_file.c:164)
[    1.296493]  full_proxy_read (fs/debugfs/file.c:378 (discriminator 1))
[    1.296658]  vfs_read (fs/read_write.c:572)
[    1.296981]  ksys_read (fs/read_write.c:717)
[    1.297132]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
[    1.297325]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

Add a NULL check and print "(none)" for entries with no assigned slave.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ caafa84251b886feb6cdf23d50e2cc99dcdaaaf3; < 19f0fd87df0e5746b24f5caa465a66a8c6e6e241 (affected, git); ≥ caafa84251b886feb6cdf23d50e2cc99dcdaaaf3; < edacf1613f7b26423ebfa8b2892e7453c4235354 (affected, git); ≥ caafa84251b886feb6cdf23d50e2cc99dcdaaaf3; < 2ec2c777f357a83c3d503d8d9370c90b60f0ae63 (affected, git); ≥ caafa84251b886feb6cdf23d50e2cc99dcdaaaf3; < 0a3f8cd3f370247ded14d38d216b49dd30eade76 (affected, git); ≥ caafa84251b886feb6cdf23d50e2cc99dcdaaaf3; < 6a3bb74e25d79cbb15f67ef80f71e2b2bfe27ff4 (affected, git); ≥ caafa84251b886feb6cdf23d50e2cc99dcdaaaf3; < 017d674cf6930e9586a29ee808c7ca09d1396d07 (affected, git); ≥ caafa84251b886feb6cdf23d50e2cc99dcdaaaf3; < ec9762f0df2f9fbe3f40a3bfa8aab8b2f721466c (affected, git); ≥ caafa84251b886feb6cdf23d50e2cc99dcdaaaf3; < 605b52497bf89b3b154674deb135da98f916e390 (affected, git). Source: CNA: Linux
- Linux / Linux: 2.6.38 (affected); ≥ 0; < 2.6.38 (unaffected, semver); ≥ 5.10.253; ≤ 5.10.* (unaffected, semver); ≥ 5.15.203; ≤ 5.15.* (unaffected, semver); ≥ 6.1.167; ≤ 6.1.* (unaffected, semver); ≥ 6.6.130; ≤ 6.6.* (unaffected, semver); ≥ 6.12.78; ≤ 6.12.* (unaffected, semver); ≥ 6.18.20; ≤ 6.18.* (unaffected, semver); ≥ 6.19.10; ≤ 6.19.* (unaffected, semver); ≥ 7.0; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.5; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP: ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP: ≥ V3.1.5; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP: ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.5; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.13% as of 2026-11-05; percentile 2.54%

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

- Weaknesses: Not reported

## Exploit evidence

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

## References

- https://git.kernel.org/stable/c/19f0fd87df0e5746b24f5caa465a66a8c6e6e241 (CNA: Linux)

- https://git.kernel.org/stable/c/edacf1613f7b26423ebfa8b2892e7453c4235354 (CNA: Linux)

- https://git.kernel.org/stable/c/2ec2c777f357a83c3d503d8d9370c90b60f0ae63 (CNA: Linux)

- https://git.kernel.org/stable/c/0a3f8cd3f370247ded14d38d216b49dd30eade76 (CNA: Linux)

- https://git.kernel.org/stable/c/6a3bb74e25d79cbb15f67ef80f71e2b2bfe27ff4 (CNA: Linux)

- https://git.kernel.org/stable/c/017d674cf6930e9586a29ee808c7ca09d1396d07 (CNA: Linux)

- https://git.kernel.org/stable/c/ec9762f0df2f9fbe3f40a3bfa8aab8b2f721466c (CNA: Linux)

- https://git.kernel.org/stable/c/605b52497bf89b3b154674deb135da98f916e390 (CNA: Linux)

- https://cert-portal.siemens.com/productcert/html/ssa-082556.html (ADP: siemens-SADP)

- 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)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-31546; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-31546; retrieved 2026-11-05; source updated Not reported

Revision: 61fbcb0d335dc02c459bf460aa5c980e07628d9ceea6fb6fcef847c32ce0c387

Canonical: https://y2.dev/cve/CVE-2026-31546

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