Linux Kernel: NULL Pointer Dereference (CVE-2026-45842)
Published Last modified Sources: Debian LTS, SUSE, Ubuntu, Siemens ProductCERT, Debian, BSI, Msrc Update Guide, CVE.org, EUVD
What is affected, what to do
In the Linux kernel, the following vulnerability has been resolved: slip: reject VJ receive packets on instances with no rstate array slhc_init() accepts rslots == 0 as a valid configuration, with the documented meaning of 'no receive compression'. In that case the allocation loop in slhc_init() is skipped, so comp->rstate stays NULL and comp->rslot_limit stays 0 (from the kzalloc of struct slcompress).
The available sources name no fixed version. Check the vendor guidance in the references below.
Conflicting version data — version display is hidden until the data is resolved.
Not sure whether and how you are affected? Ask a question about this vulnerability
Metrics
5.5
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
5.5
CVSS v3
Severity Medium on the scale from 0 to 10.
Source: Debian LTS, SUSE, Ubuntu, Siemens ProductCERT, Debian, BSI, Msrc Update Guide, CVE.org, EUVD
0.1 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 2.6
Show all metrics
- Severity
- Medium
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 45.52 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 5.5 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 5.5
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.1 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 2.6
- Low — this CVE sits in the lower 10% of all CVEs scored today.
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
In the Linux kernel, the following vulnerability has been resolved: slip: reject VJ receive packets on instances with no rstate array slhc_init() accepts rslots == 0 as a valid configuration, with the documented meaning of 'no receive compression'. In that case the allocation loop in slhc_init() is skipped, so comp->rstate stays NULL and comp->rslot_limit stays 0 (from the kzalloc of struct slcompress). The receive helpers do not defend against that configuration. slhc_uncompress() dereferences comp->rstate[x] when the VJ header carries an explicit connection ID, and slhc_remember() later assigns cs = &comp->rstate[...] after only comparing the packet's slot number to comp->rslot_limit. Because rslot_limit is 0, slot 0 passes the range check, and the code dereferences a NULL rstate. The configuration is reachable in-tree through PPP. PPPIOCSMAXCID stores its argument in a signed int, and (val >> 16) uses arithmetic shift. Passing 0xffff0000 therefore sign-extends to -1, so val2 + 1 is 0 and ppp_generic.c ends up calling slhc_init(0, 1). Because /dev/ppp open is gated by ns_capable(CAP_NET_ADMIN), the whole path is reachable from an unprivileged user namespace. Once the malformed VJ state is installed, any inbound VJ-compressed or VJ-uncompressed frame that selects slot 0 crashes the kernel in softirq context: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:slhc_uncompress (drivers/net/slip/slhc.c:519) Call Trace: <TASK> ppp_receive_nonmp_frame (drivers/net/ppp/ppp_generic.c:2466) ppp_input (drivers/net/ppp/ppp_generic.c:2359) ppp_async_process (drivers/net/ppp/ppp_async.c:492) tasklet_action_common (kernel/softirq.c:926) handle_softirqs (kernel/softirq.c:623) run_ksoftirqd (kernel/softirq.c:1055) smpboot_thread_fn (kernel/smpboot.c:160) kthread (kernel/kthread.c:436) ret_from_fork (arch/x86/kernel/process.c:164) </TASK> Reject the receive side on such instances instead of touching rstate. slhc_uncompress() falls through to its existing 'bad' label, which bumps sls_i_error and enters the toss state. slhc_remember() mirrors that with an explicit sls_i_error increment followed by slhc_toss(); the sls_i_runt counter is not used here because a missing rstate is an internal configuration state, not a runt packet. The transmit path is unaffected: the only in-tree caller that picks rslots from userspace (ppp_generic.c) still supplies tslots >= 1, and slip.c always calls slhc_init(16, 16), so comp->tstate remains valid and slhc_compress() continues to work.
Source: Debian LTS Advisories, suse_csaf, Ubuntu Security Notices, siemens_advisory, Debian Security Advisories, BSI WID Portal, BSI CSAF, Microsoft Security Update Guide, cvelistv5, NVD (NIST), ENISA EUVD, CVE.org (MITRE)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Linux | Linux |
|
|
| Siemens | SIMATIC S7 |
|
|
Vendors and products
Affected operating systems
| Linux | debian | linux | bookworm |
| Linux | debian | linux | bullseye |
| Linux | debian | linux | trixie |
| Linux | debian | linux-6.1 | bullseye |
| Linux | ubuntu | linux-oracle-7.0 | noble |
| Linux | linux | linux_kernel | — |
References & sources
- git.kernel.orgstable/c/c6980e8b1a86288167f34966fa5219031999b6f1euvd
- git.kernel.orgstable/c/de42f86e2cf5028a97e74c25869d1a962b13c301euvd
- git.kernel.orgstable/c/9e1ff0eead073c4f46d874ad2526b7dda5465fafeuvd
- git.kernel.orgstable/c/7b0d9e878ec2b21d99ae8051b3dda59cdb66c152euvd
- git.kernel.orgstable/c/e76607442d5b73e1ba6768f501ef815bb58c2c0eeuvd
- git.kernel.orgstable/c/3d71c961febddd855d3ae9a519eeb96c8023f430
- git.kernel.orgstable/c/72304fec672e8aac9ee7b9c475db96b37cca8d8d
- git.kernel.orgstable/c/4aa9eca6fda2919027dfd7a7cc69334982d89586
- Siemens ProductCERTproductcert/html/ssa-784472.html
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Record modifiedLinux
New references:- https://git.kernel.org/stable/c/3d71c961febddd855d3ae9a519eeb96c8023f430
- https://git.kernel.org/stable/c/4aa9eca6fda2919027dfd7a7cc69334982d89586
- https://git.kernel.org/stable/c/72304fec672e8aac9ee7b9c475db96b37cca8d8d
- https://git.kernel.org/stable/c/7b0d9e878ec2b21d99ae8051b3dda59cdb66c152
and 4 more references
Show 24 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://git.kernel.org/stable/c/3d71c961febddd855d3ae9a519eeb96c8023f430Reference added —https://git.kernel.org/stable/c/4aa9eca6fda2919027dfd7a7cc69334982d89586Reference added —https://git.kernel.org/stable/c/72304fec672e8aac9ee7b9c475db96b37cca8d8dReference added —https://git.kernel.org/stable/c/7b0d9e878ec2b21d99ae8051b3dda59cdb66c152Reference added —https://git.kernel.org/stable/c/9e1ff0eead073c4f46d874ad2526b7dda5465fafReference added —https://git.kernel.org/stable/c/c6980e8b1a86288167f34966fa5219031999b6f1Reference added —https://git.kernel.org/stable/c/de42f86e2cf5028a97e74c25869d1a962b13c301Reference added —https://git.kernel.org/stable/c/e76607442d5b73e1ba6768f501ef815bb58c2c0eReference removed https://git.kernel.org/stable/c/3d71c961febddd855d3ae9a519eeb96c8023f430—Reference removed https://git.kernel.org/stable/c/4aa9eca6fda2919027dfd7a7cc69334982d89586—Reference removed https://git.kernel.org/stable/c/72304fec672e8aac9ee7b9c475db96b37cca8d8d—Reference removed https://git.kernel.org/stable/c/7b0d9e878ec2b21d99ae8051b3dda59cdb66c152—Reference removed https://git.kernel.org/stable/c/9e1ff0eead073c4f46d874ad2526b7dda5465faf—Reference removed https://git.kernel.org/stable/c/c6980e8b1a86288167f34966fa5219031999b6f1—Reference removed https://git.kernel.org/stable/c/de42f86e2cf5028a97e74c25869d1a962b13c301—Reference removed https://git.kernel.org/stable/c/e76607442d5b73e1ba6768f501ef815bb58c2c0e—Reference type removed https://git.kernel.org/stable/c/3d71c961febddd855d3ae9a519eeb96c8023f430 Types: Patch—Reference type removed https://git.kernel.org/stable/c/4aa9eca6fda2919027dfd7a7cc69334982d89586 Types: Patch—Reference type removed https://git.kernel.org/stable/c/72304fec672e8aac9ee7b9c475db96b37cca8d8d Types: Patch—Reference type removed https://git.kernel.org/stable/c/7b0d9e878ec2b21d99ae8051b3dda59cdb66c152 Types: Patch—Reference type removed https://git.kernel.org/stable/c/9e1ff0eead073c4f46d874ad2526b7dda5465faf Types: Patch—Reference type removed https://git.kernel.org/stable/c/c6980e8b1a86288167f34966fa5219031999b6f1 Types: Patch—Reference type removed https://git.kernel.org/stable/c/de42f86e2cf5028a97e74c25869d1a962b13c301 Types: Patch—Reference type removed https://git.kernel.org/stable/c/e76607442d5b73e1ba6768f501ef815bb58c2c0e Types: Patch—Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Record modifiedSiemens ADP
Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/45xxx/CVE-2026-45842.json">CVE-2026-45842</a>Reference added —https://cert-portal.siemens.com/productcert/html/ssa-784472.htmlSource identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
Embed badge
Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.
<a href="https://intel.neosec.eu/en/cve/CVE-2026-45842"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-45842.svg?lang=en" alt="CVE-2026-45842 – NEOSEC Intel" height="20"></a>