Bug 2520980 (CVE-2026-74581)
| Summary: | CVE-2026-74581 kernel: net: ipv6: use-after-free in fib6_rule_suppress due to stale res->rt6 pointer | ||
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| Product: | [Other] Security Response | Reporter: | OSIDB Bzimport <bzimport> |
| Component: | vulnerability | Assignee: | Product Security <prodsec-ir-bot> |
| Status: | NEW --- | QA Contact: | |
| Severity: | high | Docs Contact: | |
| Priority: | high | ||
| Version: | unspecified | CC: | akito5623, mleitner, rhel-process-autobot, watson-tool-maintainers |
| Target Milestone: | --- | Keywords: | Security |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
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| Fixed In Version: | Doc Type: | --- | |
| Doc Text: |
A use-after-free vulnerability was found in the Linux kernel's IPv6 FIB rule lookup path. In fib6_rule_suppress(), when a route is suppressed and released via ip6_rt_put_flags(), the res->rt6 pointer is not cleared. If no later rule supplies a replacement route, fib6_rule_lookup() returns the stale (freed) rt6_info to its caller. The subsequent dst_release() then operates on freed memory, hitting rcuref_put_slowpath(). A local attacker who can configure IPv6 routing/FIB rules could trigger this to cause a denial of service (kernel crash) or potentially escalate privileges.
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Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | Type: | --- | |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
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Description
OSIDB Bzimport
2026-08-21 12:57:57 UTC
Upstream advisory: https://lore.kernel.org/linux-cve-announce/2026082100-CVE-2026-74581-47ca@gregkh/T/#u The proposed mitigation does not appear to be applicable to the affected RHEL kernels because IPv6 is built directly into the kernel (`CONFIG_IPV6=y`), rather than provided as a loadable kernel module. Therefore, the following configuration cannot prevent the IPv6 subsystem from being loaded: install ipv6 /bin/true blacklist ipv6 Since there is no `ipv6.ko` module to blacklist when `CONFIG_IPV6=y`, this mitigation would not disable the vulnerable IPv6 code path. A kernel command-line parameter such as: ipv6.disable=1 would appear to be a more appropriate mitigation for completely disabling IPv6 on these kernels. Could you please confirm whether the current mitigation guidance is correct for RHEL kernels built with `CONFIG_IPV6=y`? |