How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

417,459

Total vulnerabilities in the database

CVE-2026-98158 — linux / linux_kernel

Out-of-bounds Read

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

ppp_async: drop the errored frame instead of resetting its headroom

ppp_receive_nonmp_frame() prepends a two-byte direction tag before running the pass/active BPF filters:

*(__be16 *)skb_push(skb, 2) = htons(PPP_FILTER_INBOUND_TAG);

Nothing on the receive path guarantees those two bytes of headroom. The frame-error path in ppp_async's process_input_packet() resets a reused skb's headroom to zero while claiming to restore it to a freshly allocated state - but a fresh skb from dev_alloc_skb() carries NET_SKB_PAD:

err:
	if (skb) {
		/* make skb appear as freshly allocated */
		skb_trim(skb, 0);
		skb_reserve(skb, - skb_headroom(skb));
	}

ap->rpkt still points at that skb, so the next frame is reassembled into it with no headroom at all. A peer that sends a bad-FCS frame followed by one beginning ff 03 then leaves a single byte of headroom by the time the filter tag is pushed, which lands one byte below skb->head:

skbuff: skb_under_panic: len:49 put:2 head:ffff888003c10000 data:ffff888003c0ffff tail:0x30 end:0x640 dev:<NULL> kernel BUG at net/core/skbuff.c:214! RIP: 0010:skb_panic+0x13e/0x230 Call Trace: skb_push+0xbd/0x100 ppp_receive_nonmp_frame+0x48a/0x1d10 ppp_input+0x4e9/0x2f80 ppp_async_process+0x2a/0xe0 tasklet_action_common+0x20f/0x8a0 handle_softirqs+0x18e/0x590 Kernel panic - not syncing: Fatal exception in interrupt

Zeroing the headroom violates the NET_SKB_PAD guarantee that dev_alloc_skb() gives the rest of the receive path. Besides the filter panic above, when CCP compression is enabled ppp_decompress_frame() hands skb->data - 2 to ->decompress()/->incomp(), which then reads out of bounds before skb->head for the same reason.

Rather than restore the headroom, drop the errored frame - as ppp_synctty already does on its error path - and clear ap->rpkt so the next frame is reassembled into a fresh skb with proper headroom. This is simpler and fixes both the filter under-panic and the CCP out-of-bounds read.

The original V1 of this patch made room in ppp_receive_nonmp_frame() with skb_cow_head(); Eric pointed out that fixing the root cause in the transport is the right approach.

Found by fuzzing the PPP receive path with a mutating peer on a pty; it is an interesting (remote) DoS: root configures PPP, the peer supplies two crashing frames. The reproducer (repro-ppp-skb.c, unchanged from v1) panics in about a second, and returns cleanly with this applied.

Published: Sep 25, 2026
Updated: Nov 12, 2026
CVE: CVE-2026-98158
Severity: Medium
Exploit:
CISA KEV:

CVSS v3:

Severity: Medium
Score: 5.5
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CWEs:

CWE-125

Affected Software
References

Software	Affected versions
linux / linux_kernel	`>= 2.6.15, < 5.10.271`
linux / linux_kernel	`>= 5.15, < 5.15.222`
linux / linux_kernel	`>= 6.1, < 6.1.189`
linux / linux_kernel	`>= 6.6, < 6.6.158`
linux / linux_kernel	`>= 6.12, < 6.12.111`
linux / linux_kernel	`>= 6.13, < 6.18.53`
linux / linux_kernel	`>= 6.19, < 7.2.7`
linux / linux_kernel	`= 7.3-rc1`
linux / linux_kernel	`= 7.3-rc2`

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.