Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2026-43500 is a high-severity Out-of-bounds Write (CWE-787) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 0.2% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-16 (Memory Protection) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
The vulnerability CVE-2026-43500 is an out-of-bounds write (CWE-787) in the Linux kernel's rxrpc subsystem. The DATA-packet handler in rxrpc_input_call_event() and the RESPONSE handler in rxrpc_verify_response() only copy an skb to a linear buffer before invoking security operations when skb_cloned() is true. Packets carrying externally owned paged fragments—such as those with SKBFL_SHARED_FRAG set via splice() into a UDP socket or chained via skb_has_frag_list()—bypass this path and reach in-place AEAD/skcipher decryption through skb_to_sgvec(), binding shared frag pages directly into the scatter-gather list.
A local attacker with low privileges can trigger the flaw by delivering RXRPC DATA or RESPONSE packets that contain such shared fragments, or by using splice() and related socket operations to introduce them. Successful exploitation results in memory corruption that can yield arbitrary code execution or privilege escalation on the affected system.
Patches merged into mainline and stable kernels extend the unshare gate to also test skb_has_frag_list() and skb_has_shared_frag(), preserving the zero-copy fast path only for kernel-private fragments such as those from page_pool or GRO while reusing existing OOM and trace handling.
The associated EPSS score has risen to a peak of 0.4354 (current 0.4027), indicating material post-disclosure exploitation interest.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-29037
Vulnerability Data
In the Linux kernel, the following vulnerability has been resolved: rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present The DATA-packet handler in rxrpc_input_call_event() and the RESPONSE handler in rxrpc_verify_response() copy the skb to a linear one before calling…
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into the security ops only when skb_cloned() is true. An skb that is not cloned but still carries externally-owned paged fragments (e.g. SKBFL_SHARED_FRAG set by splice() into a UDP socket via __ip_append_data, or a chained skb_has_frag_list()) falls through to the in-place decryption path, which binds the frag pages directly into the AEAD/skcipher SGL via skb_to_sgvec(). Extend the gate to also unshare when skb_has_frag_list() or skb_has_shared_frag() is true. This catches the splice-loopback vector and other externally-shared frag sources while preserving the zero-copy fast path for skbs whose frags are kernel-private (e.g. NIC page_pool RX, GRO). The OOM/trace handling already in place is reused.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 4 hardening rules · 4 OS baselines
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Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation (including fuzzing and bounds checks) finds out-of-bounds write flaws before deployment.
Memory-protection mechanisms block unauthorized writes to arbitrary locations even if a write-what-where primitive exists.
Requiring documented secure-development standards and tools can mandate bounds-checked coding practices that avoid the weakness.
Secure engineering principles require memory-safe coding and bounds checking that eliminate the root cause of write-what-where flaws.
Process isolation confines the blast radius of an arbitrary write so it cannot affect other domains.
Input validation can structurally reject or sanitize data that would otherwise trigger an out-of-bounds write.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure-development practices (static analysis, bounds checking, code review) are the primary means of preventing out-of-bounds writes.
Vulnerability scanning and recording can discover out-of-bounds write flaws so they can be remediated.
Patching or replacing vulnerable software directly eliminates known instances of this coding weakness.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance can detect and prevent out-of-bounds write defects.
Secure development life cycle mandates practices that prevent out-of-bounds writes.
Application security requirements can specify bounds-checking and safe memory handling.
Secure architecture and engineering principles reduce the likelihood of buffer overflows.
Secure coding directly addresses out-of-bounds writes through language choice and coding standards.
Change management can enforce review gates that catch unsafe memory operations before deployment.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- V-248592 OL 8 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-123
RHEL 8 (1 rule)
- V-230279 RHEL 8 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-123
Windows 10 (1 rule)
- V-220727 Structured Exception Handling Overwrite Protection (SEHOP) must be enabled. prevents CWE-123
Windows 11 (1 rule)
- V-253284 Structured Exception Handling Overwrite Protection (SEHOP) must be enabled. prevents CWE-123