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Azure kernel 6.6.157.1-1 can cause crash
published 7 days ago
Summary
A coding error in the network routing component of the Azure Linux kernel can cause a division-by-zero situation, which may crash or freeze the system. This problem exists in version 6.6.157.1-1 of the kernel. Install the latest kernel update that includes the fix to prevent the issue.
What to do
The CVE record does not list a fixed version. Check the vendor's site or the advisory links below - a fix may already be released.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| Azure Linux:3 | azure | kernel | <= 6.6.157.1-1 |
Original advisory text
CVE-2026-99121 affecting package kernel 6.6.157.1-1
In the Linux kernel, the following vulnerability has been resolved:
ipv4: avoid divide by zero in fib_rebalance
fib_rebalance() computes the total eligible nexthop weight in one pass
and programs upper bounds in a second pass. A concurrent change to
ignore_routes_with_linkdown can make the first pass return zero while
the second pass sees an eligible nexthop, resulting in division by zero.
If the first pass reports a zero total, set each nexthop upper bound to
-1 and skip the division. This matches the IPv6 fix in commit
d2c26c2911dd ("ipv6: avoid divide by zero in rt6_multipath_rebalance")
and preserves the lock-free rebalance path.
ipv4: avoid divide by zero in fib_rebalance
fib_rebalance() computes the total eligible nexthop weight in one pass
and programs upper bounds in a second pass. A concurrent change to
ignore_routes_with_linkdown can make the first pass return zero while
the second pass sees an eligible nexthop, resulting in division by zero.
If the first pass reports a zero total, set each nexthop upper bound to
-1 and skip the division. This matches the IPv6 fix in commit
d2c26c2911dd ("ipv6: avoid divide by zero in rt6_multipath_rebalance")
and preserves the lock-free rebalance path.
References
Timeline
Published28 Oct 2026
Updated29 Oct 2026
First seen29 Oct 2026
Sources
AZL-111221 · OSV
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