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CVE-2026-74550
net: do not send ICMP/NDISC Redirects when peer allocation fails
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/ipv4. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74550 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When inet_getpeer_v4() or inet_getpeer_v6() fails to allocate a peer entry under memory pressure or tree size caps, redirect handlers previously fell back to sending un-rate-limited ICMP/NDISC Redirect messages. In IPv4, ip_rt_send_redirect() called icmp_send() directly when peer == NULL. In IPv6, ip6_forward() and ndisc_send_redirect() passed a NULL peer into inet_peer_xrlim_allow(), which returned true when peer == NULL. Because ICMP/NDISC Redirects are not part of the default global rate limit mask (sysctl_icmp_ratemask), sending redirects when peer == NULL creates an un-rate-limited ICMP packet storm. Fix this by failing closed in ip_rt_send_redirect(), ip6_forward(), and ndisc_send_redirect() when peer is NULL.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/ipv4/route.c
net/ipv6/ip6_output.c
net/ipv6/ndisc.c
- What this is
- NETWORKING [IPv4/IPv6]MAINTAINERS section matched on net/ipv4/route.c · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_INET /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12y
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_INET
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.48%, higher than 39.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/ipv4
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.39 | 6.1.183 | c0adf8b4247b |
| 2.6.39 | 6.6.151 | f5ecaa7ea768 |
| 2.6.39 | 6.12.103 | 21666f7af49a |
| 2.6.39 | 6.18.44 | 5ec5f00fc606 |
| 2.6.39 | 7.1.8 | 828f6670d110 |
| 2.6.39 | 7.2 | dbc3791e3b24 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- The flaw is in IPv4/IPv6 packet forwarding paths (ip_forward/ip6_forward) reached when a remote host sends IP traffic processed by a forwarding router; this is standard net stack input handling, not a local-only API.
- AC:LAttack complexity, low
- An attacker can reliably trigger redirect-eligible forwarded packets, flood unique source/destination addresses to stress inet_peer allocation, and induce memory pressure so peer allocation fails, controlling the conditions needed for the un-rate-limited redirect storm.
- PR:NPrivileges required, none
- Exploitation requires only the ability to send IP packets to a forwarding host; no local account, capabilities, or authentication on the victim is needed.
- UI:NUser interaction, none
- No victim user action is required; the redirect storm is triggered entirely by attacker-sent network packets processed during kernel forwarding.
- S:UScope, unchanged
- Impact is confined to the kernel/network stack of the targeted forwarding system and its network availability; it does not cross VM, container, or IOMMU security boundaries.
- C:NConfidentiality impact, none
- The bug bypasses redirect rate limiting to generate ICMP/NDISC storms; it does not involve memory corruption, out-of-bounds access, or unintended disclosure of sensitive kernel memory.
- I:NIntegrity impact, none
- The vulnerability causes excessive transmission of otherwise-valid redirect messages; it does not grant arbitrary data modification, code execution, or attacker-controlled corruption of kernel or application state.
- A:HAvailability impact, high
- When peer allocation fails, ICMP/NDISC Redirects are sent without any rate limit (excluded from sysctl_icmp_ratemask), enabling a sustained packet storm that can exhaust CPU, memory, and bandwidth and deny service to the router and adjacent networks.