Linux Kernel Missing Initialization of a Variable Vulnerability
In the Linux kernel, the following vulnerability has been resolved: net: skbuff: preserve shared-frag marker during coalescing skb_try_coalesce() can attach paged frags from @from to @to. If @from has SKBFL_SHARED_FRAG set, the…
Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.
Exploitation probability EPSS · FIRST
Exploitation signals 3 / 5
- KEV catalog (CISA)28 Oct 2026
- Exploited in EUVD (ENISA)28 Oct 2026
- Used by ransomwareno
- EPSS above 10 %16.1%
- No account, over the networkno
What to do
Fix
Apply the vendor’s fix as soon as it is available.
CISA guidance: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Meanwhile
Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.
Manufacturers (CRA)
Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained
Description ENISA EUVD
In the Linux kernel, the following vulnerability has been resolved: net: skbuff: preserve shared-frag marker during coalescing skb_try_coalesce() can attach paged frags from @from to @to. If @from has SKBFL_SHARED_FRAG set, the resulting @to skb can contain the same externally-owned or page-cache-backed frags, but the shared-frag marker is currently lost. That breaks the invariant relied on by later in-place writers. In particular, ESP input checks skb_has_shared_frag() before deciding whether an uncloned nonlinear skb can skip skb_cow_data(). If TCP receive coalescing has moved shared frags into an unmarked skb, ESP can see skb_has_shared_frag() as false and decrypt in place over page-cache backed frags. Propagate SKBFL_SHARED_FRAG when skb_try_coalesce() transfers paged frags. The tailroom copy path does not need the marker because it copies bytes into @to's linear data rather than transferring frag descriptors.
Affected products
- cef401de7be8c4e155c6746bfccf721a4fa5fab9 <2f2b16022a2e10ca7bccfb98db5ed2ec0f72641c
- cef401de7be8c4e155c6746bfccf721a4fa5fab9 <f84eca5817390257cef78013d0112481c503b4a3
- patch: 6.18.33
- cef401de7be8c4e155c6746bfccf721a4fa5fab9 <760e1addc27ba1a7beb4a0a7e8b3e9ec49e7a34e
- cef401de7be8c4e155c6746bfccf721a4fa5fab9 <78bf6b6bb19541d19fbda6242e7cfe2c682763c0
- patch: 0
- patch: 7.1
- patch: 6.1.174
- cef401de7be8c4e155c6746bfccf721a4fa5fab9 <9d3e5fd19fe1063bf607219e8562fbd567b8e8d5
- cef401de7be8c4e155c6746bfccf721a4fa5fab9 <3884358a9286b17f389a72b1426fc4547c23c111
- patch: 7.0.10
- 3.9
Open source packages OSV
Affected libraries according to OSV, with fixed versions.
Timeline
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Published
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Exploitation reported (ENISA)
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Added to the KEV catalog
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EPSS peak: 16.1%
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CISA remediation due date
References
Other exploited vulnerabilities from the same vendor
- CVE-2026-53266Linux Kernel Out-of-Bounds Write Vulnerability4.7 · Actively exploited
- CVE-2025-39964Linux Kernel Race Condition Vulnerability4.4 · Actively exploited
- CVE-2025-39682Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability5.8 · Actively exploited
- CVE-2026-53362Linux Kernel Unspecified Vulnerability4.3 · Actively exploited
- CVE-2022-0995Linux Kernel Out-of-Bounds Write Vulnerability4.6 · Actively exploited
- CVE-2022-0492Linux Kernel Improper Authentication Vulnerability4.5 · Actively exploited