# CVE-2026-52998: netfilter: nfnetlink_osf: fix potential NULL dereference in ttl check

Status: published. Published: 2026-06-24. Updated: 2026-11-10.

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

netfilter: nfnetlink_osf: fix potential NULL dereference in ttl check

The nf_osf_ttl() function accessed skb->dev to perform a local interface
address lookup without verifying that the device pointer was valid.

Additionally, the implementation utilized an in_dev_for_each_ifa_rcu
loop to match the packet source address against local interface
addresses. It assumed that packets from the same subnet should not see a
decrement on the initial TTL. A packet might appear it is from the same
subnet but it actually isn't especially in modern environments with
containers and virtual switching.

Remove the device dereference and interface loop. Replace the logic with
a switch statement that evaluates the TTL according to the ttl_check.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384; < f4de0777e4554a7de19c920accde6319dd530782 (affected, git); ≥ 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384; < c996a90f3071cf43683e5423da31aadbe002b8b4 (affected, git); ≥ 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384; < edc806f9122961f0d3819f7c69c14cccde31f277 (affected, git); ≥ 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384; < 5d05de2f0928d81309a815ecc76d1a3ad72cbc16 (affected, git); ≥ 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384; < 95be653a76793856ff8b2d8bd82c2943c23f5ca8 (affected, git); ≥ 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384; < 79b90a96688e521771fa6ed3dc7864b76b8df293 (affected, git); ≥ 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384; < 83fc5dd63455a779ea2dd0f7ffee3c920919d80b (affected, git); ≥ 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384; < 711987ba281fd806322a7cd244e98e2a81903114 (affected, git). Source: CNA: Linux
- Linux / Linux: 2.6.31 (affected); ≥ 0; < 2.6.31 (unaffected, semver); ≥ 5.10.258; ≤ 5.10.* (unaffected, semver); ≥ 5.15.209; ≤ 5.15.* (unaffected, semver); ≥ 6.1.175; ≤ 6.1.* (unaffected, semver); ≥ 6.6.141; ≤ 6.6.* (unaffected, semver); ≥ 6.12.91; ≤ 6.12.* (unaffected, semver); ≥ 6.18.33; ≤ 6.18.* (unaffected, semver); ≥ 7.0.10; ≤ 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 / 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: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: Linux

- CISA KEV: No listing in collected sources

- EPSS: 0.58% as of 2026-11-09; percentile 47.93%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-476

## Exploit evidence

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

## References

- https://git.kernel.org/stable/c/f4de0777e4554a7de19c920accde6319dd530782 (CNA: Linux)

- https://git.kernel.org/stable/c/c996a90f3071cf43683e5423da31aadbe002b8b4 (CNA: Linux)

- https://git.kernel.org/stable/c/edc806f9122961f0d3819f7c69c14cccde31f277 (CNA: Linux)

- https://git.kernel.org/stable/c/5d05de2f0928d81309a815ecc76d1a3ad72cbc16 (CNA: Linux)

- https://git.kernel.org/stable/c/95be653a76793856ff8b2d8bd82c2943c23f5ca8 (CNA: Linux)

- https://git.kernel.org/stable/c/79b90a96688e521771fa6ed3dc7864b76b8df293 (CNA: Linux)

- https://git.kernel.org/stable/c/83fc5dd63455a779ea2dd0f7ffee3c920919d80b (CNA: Linux)

- https://git.kernel.org/stable/c/711987ba281fd806322a7cd244e98e2a81903114 (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)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-52998; retrieved 2026-11-10; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-52998; retrieved 2026-11-10; source updated Not reported

Revision: 6d604f0a669a104ea0cdd026bf28deeea24b2acbf8b234cc9391c73cc0279e41

Canonical: https://y2.dev/cve/CVE-2026-52998

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