ESB-2026.4890

=========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2026.4890 K000161181: Linux kernel vulnerabilities CVE-2026-43284 and CVE-2026-43500 (Dirty Frag) 11 May 2026 =========================================================================== AUSCERT Security Bulletin Summary --------------------------------- Product: Linux kernel Publisher: F5 Networks Operating System: F5 Resolution: Patch/Upgrade CVE Names: CVE-2026-43284 CVE-2026-43500 Original Bulletin: https://my.f5.com/manage/s/article/K000161181 Comment: CVSS (Max): None available when published EPSS (Max): 0.0% (0th)* CVE-2026-43284 2026-05-10 * Not all EPSS found when published - --------------------------BEGIN INCLUDED TEXT-------------------- K000161181: Linux kernel vulnerabilities CVE-2026-43284 and CVE-2026-43500 (Dirty Frag) Published Date: May 8, 2026 Security Advisory Description o CVE-2026-43284 (Dirty Frag) In the Linux kernel, the following vulnerability has been resolved: xfrm: esp: avoid in-place decrypt on shared skb frags MSG_SPLICE_PAGES can attach pages from a pipe directly to an skb. TCP marks such skbs with SKBFL_SHARED_FRAG after skb_splice_from_iter(), so later paths that may modify packet data can first make a private copy. The IPv4/IPv6 datagram append paths did not set this flag when splicing pages into UDP skbs. That leaves an ESP-in-UDP packet made from shared pipe pages looking like an ordinary uncloned nonlinear skb. ESP input then takes the no-COW fast path for uncloned skbs without a frag_list and decrypts in place over data that is not owned privately by the skb. Mark IPv4/IPv6 datagram splice frags with SKBFL_SHARED_FRAG, matching TCP. Also make ESP input fall back to skb_cow_data() when the flag is present, so ESP does not decrypt externally backed frags in place. Private nonlinear skb frags still use the existing fast path. This intentionally does not change ESP output. In esp_output_head(), the path that appends the ESP trailer to existing skb tailroom without calling skb_cow_data() is not reachable for nonlinear skbs: skb_tailroom() returns zero when skb->data_len is nonzero, while ESP tailen is positive. Thus ESP output will either use the separate destination-frag path or fall back to skb_cow_data(). o CVE-2026-43500 (Dirty Frag) This candidate has been reserved by a CVE Numbering Authority (CNA). This record will be updated by the assigning CNA once details are available. Learn more about the Reserved state here. Impact For products with None in the Versions known to be vulnerable column, there is no impact. For products with ** in the various columns, F5 is still researching the issue and will update this article after confirming the required information. F5 Support has no additional information about this issue. Security Advisory Status To determine if your product and version have been evaluated for this vulnerability, refer to the Evaluated products box. To determine if your release is known to be vulnerable, the components or features that are affected by the vulnerability, and for information about releases, point releases, or hotfixes that address the vulnerability, refer to the following tables. You can also use iHealth to diagnose a vulnerability for BIG-IP, BIG-IQ, and F5OS systems. For more information about using iHealth, refer to K27404821: Using F5 iHealth to diagnose vulnerabilities. For more information about security advisory versioning, refer to K51812227: Understanding security advisory versioning. In this section o BIG-IP Next o BIG-IP and BIG-IQ o F5 Distributed Cloud and NGINX Services o F5OS o NGINX o Other products BIG-IP Next +-------------+------+-----------------+----------+----------+----------------+ | | |Versions known to|Fixes |Severity/ |Vulnerable | |Product |Branch|be vulnerable^1 |introduced|CVSS score|component or | | | | |in | |feature | +-------------+------+-----------------+----------+----------+----------------+ |BIG-IP Next |All |None |Not |Not |None | |SPK | | |applicable|vulnerable| | +-------------+------+-----------------+----------+----------+----------------+ |BIG-IP Next |All |None |Not |Not |None | |CNF | | |applicable|vulnerable| | +-------------+------+-----------------+----------+----------+----------------+ |BIG-IP Next | | |Not |Not | | |for |All |None |applicable|vulnerable|None | |Kubernetes | | | | | | +-------------+------+-----------------+----------+----------+----------------+ ^1F5 evaluates only software versions that have not yet reached the End of Technical Support (EoTS) phase of their lifecycle. For more information, refer to the Security hotfixes section of K4602: Overview of the F5 security vulnerability response policy. BIG-IP and BIG-IQ Note: After a fix is introduced for a given minor branch, that fix applies to all subsequent maintenance and point releases for that branch, and no additional fixes for that branch will be listed in the table. For example, when a fix is introduced in 16.1.2.1, the fix also applies to 16.1.2.2, and all later 16.1.x releases (16.1.3.x, 16.1.4.x). For more information, refer to K51812227: Understanding security advisory versioning. +--------------+------+----------------+----------+-----------+---------------+ | | |Versions known |Fixes |Severity/ |Vulnerable | |Product |Branch|to be vulnerable|introduced|CVSS score^|component or | | | |^1 |in |2 |feature | +--------------+------+----------------+----------+-----------+---------------+ | |21.x |** |** | | | |BIG-IP (all +------+----------------+----------+ | | |modules) |17.x |** |** |** |** | | +------+----------------+----------+ | | | |16.x |** |** | | | +--------------+------+----------------+----------+-----------+---------------+ |BIG-IQ | | | | | | |Centralized |8.x |** |** |** |** | |Management | | | | | | +--------------+------+----------------+----------+-----------+---------------+ ^1F5 evaluates only software versions that have not yet reached the End of Technical Support (EoTS) phase of their lifecycle. For more information, refer to the Security hotfixes section of K4602: Overview of the F5 security vulnerability response policy. ^2Starting with the August 2024 Quarterly Security Notification, F5 will provide the CVSS v4.0 base score in addition to the CVSS v3.1 score, for first-party security issues only. The CVSS score link takes you to a resource outside of MyF5, and the content may be removed without our knowledge. For more information about how F5 uses CVSS v4.0, refer to K000140363: Overview of CVSS v4.0 in F5 security advisories. **Confirmation of vulnerability or non-vulnerability is not presently available. F5 is still researching the issue for the products indicated and will update this article with the most current information as soon as it has been confirmed. F5 Support has no additional information on this issue. F5 Distributed Cloud and NGINX Services +--------------------+-------------------+-------------------------------+ |Service |Severity/CVSS score|Vulnerable component or feature| +--------------------+-------------------+-------------------------------+ |F5 Distributed Cloud|** |** | +--------------------+-------------------+-------------------------------+ |F5 Silverline |** |** | +--------------------+-------------------+-------------------------------+ |NGINX One Console |Not vulnerable |None | +--------------------+-------------------+-------------------------------+ **Confirmation of vulnerability or non-vulnerability is not presently available. F5 is still researching the issue for the services indicated and will update this article with the most current information as soon as it has been confirmed. F5 Support has no additional information on this issue. F5OS +-------+------+-------------------+-----------+------------+-----------------+ | | |Versions known to |Fixes |Severity/ |Vulnerable | |Product|Branch|be vulnerable^1 |introduced |CVSS score^2|component or | | | | |in | |feature | +-------+------+-------------------+-----------+------------+-----------------+ |F5OS-A |1.x |** |** |** |** | +-------+------+-------------------+-----------+------------+-----------------+ |F5OS-C |1.x |** |** |** |** | +-------+------+-------------------+-----------+------------+-----------------+ ^1F5 evaluates only software versions that have not yet reached the End of Technical Support (EoTS) phase of their lifecycle. For more information, refer to the Security hotfixes section of K4602: Overview of the F5 security vulnerability response policy. ^2Starting with the August 2024 Quarterly Security Notification, F5 will provide the CVSS v4.0 base score in addition to the CVSS v3.1 score, for first-party security issues only. The CVSS score link takes you to a resource outside of MyF5, and the content may be removed without our knowledge. For more information about how F5 uses CVSS v4.0, refer to K000140363: Overview of CVSS v4.0 in F5 security advisories. **Confirmation of vulnerability or non-vulnerability is not presently available. F5 is still researching the issue for the products indicated and will update this article with the most current information as soon as it has been confirmed. F5 Support has no additional information on this issue. NGINX +-----------+------+------------------+----------+----------+-----------------+ | | |Versions known to |Fixes |Severity/ |Vulnerable | |Product |Branch|be vulnerable^1 |introduced|CVSS score|component or | | | | |in | |feature | +-----------+------+------------------+----------+----------+-----------------+ |NGINX (all |All |None |Not |Not |None | |products) | | |applicable|vulnerable| | +-----------+------+------------------+----------+----------+-----------------+ ^1F5 evaluates only software versions that have not yet reached the End of Technical Support (EoTS) phase of their lifecycle. For more information, refer to the Security hotfixes section of K4602: Overview of the F5 security vulnerability response policy. Other products +-------+------+-------------------+-----------+------------+-----------------+ | | |Versions known to |Fixes |Severity/ |Vulnerable | |Product|Branch|be vulnerable^1 |introduced |CVSS score^2|component or | | | | |in | |feature | +-------+------+-------------------+-----------+------------+-----------------+ |Traffix|5.x |** |** |** |** | |SDC | | | | | | +-------+------+-------------------+-----------+------------+-----------------+ |F5 AI |1.x |None |Not |Not |None | |Gateway| | |applicable |vulnerable | | +-------+------+-------------------+-----------+------------+-----------------+ ^1F5 evaluates only software versions that have not yet reached the End of Technical Support (EoTS) phase of their lifecycle. For more information, refer to the Security hotfixes section of K4602: Overview of the F5 security vulnerability response policy. ^2Starting with the August 2024 Quarterly Security Notification, F5 will provide the CVSS v4.0 base score in addition to the CVSS v3.1 score, for first-party security issues only. The CVSS score link takes you to a resource outside of MyF5, and the content may be removed without our knowledge. For more information about how F5 uses CVSS v4.0, refer to K000140363: Overview of CVSS v4.0 in F5 security advisories. **Confirmation of vulnerability or non-vulnerability is not presently available. F5 is still researching the issue for the products indicated and will update this article with the most current information as soon as it has been confirmed. F5 Support has no additional information on this issue. Security Advisory Recommended Actions F5 is still researching the issue for the products indicated and will update this article with the most current information as soon as it has been confirmed. F5 Support has no additional information on this issue. Related Content o K41942608: Overview of MyF5 security advisory articles o K12201527: Overview of Quarterly Security Notifications o K51812227: Understanding security advisory versioning o K4602: Overview of the F5 security vulnerability response policy o K4918: Overview of the F5 critical issue hotfix policy o K39757430: F5 product and services lifecycle policy index o K9970: Subscribe to email notifications regarding F5 products and security announcements o K9957: Creating a custom RSS feed to view new and updated documents - --------------------------END INCLUDED TEXT---------------------- You have received this e-mail bulletin as a result of your organisation's registration with AUSCERT. 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